CN110643041A

CN110643041A - Colorless transparent polyimide film with adjustable refractive index and preparation method thereof

Info

Publication number: CN110643041A
Application number: CN201911013235.3A
Authority: CN
Inventors: 王文静; 王海生
Original assignee: Hefei Zhonghuiruineng Energy Technology Co Ltd
Current assignee: Hefei Zhonghuiruineng Energy Technology Co Ltd
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-01-03

Abstract

The invention belongs to the technical field of functional films, and particularly relates to a colorless transparent polyimide film with an adjustable refractive index, which comprises a polyimide body, wherein an additive is uniformly dispersed in the polyimide body, and the additive is nano zinc oxide with the surface coated with zinc carbonate; the particle size of the nano zinc oxide is 20-120nm, and the coating thickness of the zinc carbonate is 3-25 nm; the weight of the additive accounts for 0.5 wt% -18 wt% of the total weight of the polyimide film. The invention has the beneficial effects that: by selecting the nano zinc oxide particle filler with non-axisymmetric structure appearance and specific performance parameters in the colorless transparent polyimide film, the obtained polyimide film has excellent mechanical properties, thermal properties (shrinkage rate, thermal expansion coefficient and the like) and insulating properties (electrical strength, dielectric constant and the like), and simultaneously further realizes controllable refractive index and lower birefringence parameters of the colorless transparent polyimide film, so that the requirements of the market can be met, and the application field of products can be enlarged.

Description

Colorless transparent polyimide film with adjustable refractive index and preparation method thereof

Technical Field

The invention belongs to the technical field of functional films, and particularly relates to a colorless transparent polyimide film with an adjustable refractive index and a preparation method thereof.

Background

The development of the photoelectric device in the future gradually shows the trend of light weight, large size, ultra-thin and flexibility, the glass serving as the traditional transparent substrate material cannot meet the development requirement of the flexible packaging technology in the future, and the high-transparency polymer material becomes the first choice of the flexible photoelectric packaging substrate material in the future due to the advantages of transparency, flexibility, light weight, high impact resistance and the like. The polyimide film has excellent heat-resistant stability, and can meet the requirements of high-temperature processes such as electrode film deposition, annealing treatment and the like in the processing process of photoelectric devices, so that the development of high-transparency polyimide materials becomes a key point of research. The traditional polyimide film is brown or yellow due to high aromatic ring density, has low transmittance in the range of visible light (wavelength of 400nm-700nm), and has high birefringence, so that the application of the traditional polyimide film in the advanced photoelectric field, such as optical waveguide materials, photoelectric packaging materials, photovoltaic materials, nonlinear optical materials, light refraction edge materials, photoelectric materials, orientation film materials in the liquid crystal display field and the like, is severely limited.

The existing colorless transparent polyimide film preparation technology mainly avoids or reduces conjugated units, reduces the charge transfer effect in molecules or between molecules and improves the light transmittance and transparency of the polyimide film by introducing monomers such as fluorine-containing groups, bulky substituents, alicyclic structures, main chain bending structures, asymmetric structures, conjugated double bond structures and the like. At present, researchers at home and abroad develop a new formula by adopting the structural monomers and mutually combining the structural monomers, and prepare the colorless transparent polyimide film with high light transmittance, high modulus, relatively high glass transition temperature (Tg), relatively low CTE (coefficient of thermal expansion) and low thermal shrinkage rate by methods such as block polymerization and chemical polymerization, but the improvement of the comprehensive performance of the film is limited, for example, the defects of high haze, low refractive index, high birefringence, low surface hardness and the like exist. Even if polymerization is carried out after a refining pretreatment of the polymerization monomers and the solvent, the improvement of the overall properties is greatly limited. In addition, in the prior art, some high-molar-refractive-index groups are introduced through molecular structure design, namely, the rigid chain segment is added to endow the polyimide with high refractive index, high heat-resistant stability, high mechanical property and dielectric property. Furthermore, the thermal stability and mechanical properties of the polyimide are somewhat reduced by excessive retention of the flexible links. How to expand the application field of polyimide films (especially in the fields of solar cells, liquid crystal displays, optoelectronic integrated circuits and the like) and further improve the optical properties of colorless transparent polyimide films (such as haze reduction, refractive index improvement, birefringence reduction, intrinsic surface hardness enhancement and the like) is a problem to be solved urgently by researchers at present.

Disclosure of Invention

In order to solve the above problems, the present invention provides a colorless transparent polyimide film with an adjustable refractive index, wherein a non-axisymmetric nano zinc oxide is added into a polyamic acid resin solution to prepare the colorless transparent polyimide film through extrusion casting, biaxial stretching, high temperature imidization, sizing treatment and other forming processes, and the refractive index of the transparent polyimide film is adjusted by selecting the zinc oxide coated with zinc carbonate and having specific parameters, and the transparent polyimide film has optical properties such as low haze and low birefringence. The colorless polyimide film product prepared by the method maintains the original high transparency, mechanical property and heat resistance of the film, effectively improves the optical characteristics of the intrinsic surface hardness of the film being more than 3.8H, the birefringence being less than or equal to 0.02, the haze being less than or equal to 0.2 percent and the refractive index range being controlled between 1.68 and 1.88, and realizes the multi-aspect application of the colorless transparent polyimide film in the optical field.

The invention provides a colorless transparent polyimide film with an adjustable refractive index, which comprises a polyimide body, wherein an additive is uniformly dispersed in the polyimide body, and the additive is nano zinc oxide with the surface coated with zinc carbonate;

the particle size of the nano zinc oxide is 20-120nm, and the coating thickness of the zinc carbonate is 3-25 nm;

the weight of the additive accounts for 0.5-18 wt% of the total weight of the polyimide film;

before coating the zinc carbonate on the surface of the nano zinc oxide, the nano zinc oxide is treated as follows: the high-temperature deoxidation pretreatment time is 0.5h to 3.5h at the temperature of 300 ℃ to 1000 ℃.

Preferably, the specific surface area of the nano zinc oxide is 48-350m²The pH value is 5.8-8.2, the conductivity is less than 600pS/cm, the agglomeration index is less than or equal to 50, and the refractive index is 1.9-2.1.

Preferably, the particle size of the nano zinc oxide is 25-80 nm.

Preferably, the particle size of the nano zinc oxide is 28-38 nm.

Preferably, the nano zinc oxide has a wurtzite structure and a sphalerite structure which have central symmetry and non-axial symmetry.

Preferably, the coating thickness of the zinc carbonate is 6-15 nm.

Preferably, the weight of the additive accounts for 0.8 wt% to 12 wt% of the total weight of the polyimide film.

Preferably, the weight of the additive accounts for 1 wt% to 5 wt% of the total weight of the polyimide film.

The invention also provides a preparation method of the polyimide film, which is characterized by comprising the following steps:

a. carrying out polycondensation reaction on aromatic diamine and aromatic dianhydride to obtain amino and/or anhydride group terminated polyamide acid resin;

b. coating zinc carbonate on the surface of the nano zinc oxide by adopting a physical or chemical method to obtain the additive;

c. and blending the additive and the polyamide acid resin, and then carrying out imidization treatment to obtain the polyimide film.

Preferably, the specific preparation method of the polyamic acid resin comprises the following steps of mixing aromatic diamine and aromatic dianhydride in a molar ratio (0.9-1.1): 1 is uniformly dispersed in the polar aprotic solvent and stirred for reaction for 2-24h at the speed of 100-1500r/min to obtain polyamic acid resin;

the blending condition is that the stirring reaction is carried out for 3-16h at the temperature of 15-35 ℃ and the speed of 200-;

the imidization treatment method comprises the steps of forming a product after blending into a polyamic acid resin solution film with the thickness of 20-800 mu m, drying and curing at the temperature of 100-250 ℃ for 0.1-6h, removing 20-90 wt% of solvent in the polyamic acid resin solution film to obtain the polyamic acid film with self-supporting property, and then sequentially carrying out longitudinal and transverse stretching at the temperature of 60-238 ℃ for 0.1-5.5h by 0.8-2.8 times, imidization at the temperature of 550 ℃ for 0.1-8.8h, and shaping at the temperature of 180 ℃ for 0.1-7.5h to obtain the colorless transparent polyimide film with the thickness of 2.5-120 mu m.

Preferably, the aromatic diamine is selected from the group consisting of 3,4' -diaminodiphenyl ether (3,4' -ODA), 4' -diaminodiphenyl ether (4,4' -ODA), 2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (2,2' -TFDB), 3' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (3,3' -TFDB), 4' -diaminobiphenyl, m-phenylenediamine (m-PDA), p-phenylenediamine (p-PDA), 2' -bis-trifluoromethyl-4, 4' -diaminodiphenyl ether (TFODA), 3' -diamino-5, 5 ' -bis-trifluoromethyl-biphenyl (s-TFDB), 2-bis (trifluoromethyl) -4,4 '-diaminophenylsulfone (SFTA), 4' -bis (2-trifluoromethyl-4-aminophenoxy) diphenylsulfone, 2- (4-aminophenyl) -5-aminobenzimidazole (APBIA), 4 '-bis (3-aminophenoxy) diphenylsulfone (M-BAPS), bis (3-aminophenyl) sulfone (3-DDS), bis (4-aminophenyl) sulfone (4-DDS), 4' -bis (4-aminophenoxy) biphenyl (BAPB), 1, 3-bis (3-aminophenoxy) benzene (TPE-M), 1, 3-bis (4-aminophenoxy) benzene (TPE-R), 1, 4-bis (4-aminophenoxy) benzene (TPE-Q), Any one or a combination of any more of 2,2' -bis [4- (4-aminophenoxy phenyl) ] propane (BAPP), 2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane (HFBAPP), 9-bis (3-fluoro-4-aminophenyl) fluorene (FFDA), 9-bis (3-methyl-4-aminophenyl) fluorene (BMAPF), 9-bis (4-aminophenyl) Fluorene (FDA);

the aromatic dianhydride is selected from 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA), 3,4' -hexafluoroisopropylphthalic anhydride (a-6FDA), 4- (2, 5-dioxotetrahydrofuran-3-yl) -1,2, 3, 4-tetrahydronaphthalene-1, 2-dicarboxylic anhydride (TDA), 4' - (4,4' -isopropyldiphenoxy) bis (phthalic anhydride) (HBDA), 2,3,3',4' -biphenyltetracarboxylic dianhydride (a-BPDA), 4' -triphendiether tetracarboxylic dianhydride (HQDPA), diphenylsulfide tetracarboxylic dianhydride (3,4,3',4' -TDPA, 2,3,2',3' -TDPA, 2,3,3',4'-TDPA), 2,3,3',4 '-diphenylether tetracarboxylic dianhydride (a-ODPA), 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride (BPADA), 3,3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2,3',4 '-diphenylsulfone tetracarboxylic dianhydride, pyromellitic acid (PMDA), 3,3',4,4 '-biphenyltetracarboxylic dianhydride (BPDA), 2',3,3 '-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3',4 '-benzophenonetetracarboxylic dianhydride (a-BTDA), benzophenonetetracarboxylic dianhydride (BTDA), 4,4' -Oxydiphthalic Dianhydride (ODPA) or a combination of any of them.

Preferably, the amounts of the aromatic diamine, the aromatic dianhydride and the polar aprotic solvent are controlled such that the ratio of the solid content M in the polyamic acid resin solution formed in the present step is 5 wt% to 60 wt%.

Preferably, before blending, the method further comprises the following treatment of the additive,

adding the additive into a polar aprotic solvent, and sequentially carrying out low-speed shearing stirring at 50-180r/min for 0.5-8.5h, high-speed shearing stirring pretreatment at 500-1500r/min for 0.2-10h, emulsifying treatment at 1000-1800r/min for 0.5-12h, high-pressure homogenizing treatment at 10-100MPa for 0.1-6h and ultrasonic dispersion treatment at 28-42 khz for 0.5-6 h;

the weight of the additive is 5-28 wt% of the weight of the polar aprotic solvent.

Preferably, the polar aprotic solvent is selected from any one or a combination of any more of low molecular weight carboxyamides, in particular N, N '-Dimethylacetamide (DMAC), N' -Dimethylformamide (DMF), N-methylpyrrolidone (NMP), Dimethylsulfoxide (DMSO), tetramethylsulfoxide, N '-dimethyl-N, N' -propyleneurea (DMPU), cyclopentanone, cyclohexanone, dichloromethane, monochlorobenzene, dichlorobenzene, chloroform, tetrahydrofuran, 3-methyl-N, N-dimethylpropionamide, N-dialkylcarboxyamide, m-cresol, γ -butyrolactone.

Coating zinc carbonate by physical or chemical methodThe nano zinc oxide is coated on the surface of the nano zinc oxide, and in the process of obtaining the additive, the nano zinc oxide meets the following conditions: average particle diameter of 20-120nm and specific surface area of 48-350m²The pH value is 5.8-8.2, the conductivity is less than 600pS/cm, the agglomeration index is less than or equal to 50, and the refractive index is 1.9-2.1.

More preferably, the nano zinc oxide meets the following conditions: an average particle diameter of 25nm to 80nm (more preferably 28nm to 38nm), a specific surface area of 100 to 320m²(further preferably 180- & ltwbr/& gt, 300 m)²(iv)/g), a pH of 6.2 to 8.0 (further preferably 6.5 to 7.5), an electrical conductivity of < 500pS/cm (further preferably < 400pS/cm), an agglomeration index of < 40 (further preferably < 30), and a refractive index of 1.95 to 2.05 (further preferably 1.98 to 2.00).

If the particle size of the nano zinc oxide is smaller, the aggregation phenomenon is easy to generate, the problem of uneven dispersion in the film is caused, the process operation is not easy to control, meanwhile, the photoelectric effect is weaker due to the smaller particle size, and the crystallization direction of the nano material is not suitable to control, so that the refractive index characteristic of the colorless and transparent polyimide film cannot be further effectively regulated and controlled. If the particle size of the nano zinc oxide is larger, the surface of the prepared film is too rough, the haze of the film product is larger, and the film product is not suitable for products in the photoelectron field; if the addition amount of the nano zinc oxide filler is too small, the optical performance effects such as the controllable refractive index and the birefringence are reduced; if the amount is too large, the mechanical properties, physical properties, electrical properties and other product characteristics of the colorless and transparent polyimide film are deteriorated, and uneven dispersion (sedimentation and agglomeration) is likely to occur in the polyamic acid resin, the film properties are poor in consistency, and the production cost of the film is increased.

The applicant finds in a large number of experiments, research and analysis that the traditional coloring effect of the nano zinc oxide as a white pigment can be overcome by selecting the nano zinc oxide meeting characteristic performance parameters, and the nano zinc oxide is subjected to surface coating zinc carbonate layer pretreatment to generate a surface complex compound by combining with a polyamic acid resin through a coordination bond, and the nano zinc oxide is used as a strong promoter and has a catalytic function to complete the bonding of the polyamic acid and/or polyimide body organic matter and inhibit the defects among polyamic acid and/or polyimide body molecules. Not only can make the obtained colorless transparent polyimideThe polyimide film has excellent thermal property and insulating property, and can selectively and effectively regulate and control the optical properties of the colorless transparent polyimide film, such as refractive index, birefringence and the like, the refractive index range can be effectively regulated and controlled by the thickness or coating amount of a zinc carbonate coating layer, the birefringence is kept low, and the essential reason for regulating and controlling the refractive index of the film is not that zinc oxide with relatively high refractive index is selected (only inorganic fillers with intrinsic refractive index higher than that of zinc oxide are more, such as ZrO, for example)₂、TiO₂PbS, etc.) and the zinc oxide is coated with zinc carbonate with a certain thickness on the surface of the zinc oxide on the basis of high-temperature pretreatment. In addition, the PH value of the zinc oxide is limited, the oxidizability and interface combination property of the zinc oxide inorganic filler which is pretreated at high temperature and coats the zinc carbonate in polar solvent-containing polyamide acid resin can be effectively adjusted in a required PH value range, the zinc oxide inorganic filler which is pretreated at high temperature and coats the zinc carbonate has high dispersion uniformity in the polyamide acid resin, can promote dehydration and cyclization of polyamide acid molecules and inhibit oxidation to a certain extent, forms a transitional unstable complex intermediate with the dehydrated molecules and the carboxyl hydroxyl in the polyamide acid molecules, generates a synergistic effect with the polyimide molecules at an interface position through subsequent high-temperature imidization treatment, further promotes the zinc oxide inorganic filler which coats the zinc carbonate to migrate and recombine in a polyimide matrix, and is pretreated at high temperature and coated with the zinc carbonate on the surface under the condition that the thermal reaction kinetics principle is combined with the enhanced optical property The refractive index and the intrinsic surface hardness of the colorless transparent polyimide film are effectively improved, and the birefringence and other characteristics are reduced. Furthermore, under the specific parameters such as conductivity, agglomeration index and the like and the synergistic effect thereof, the nano zinc oxide can be uniformly dispersed in the polyimide basic resin system without adding a dispersing agent or a coupling agent. The nano zinc oxide has a hexagonal wurtzite structure, a cubic sphalerite structure and a sodium chloride type octahedral structure; more preferably, the structure is a wurtzite structure and a sphalerite structure which have central symmetry and non-axial symmetry; further preferably large energy band gap and exciton binding energy, and transparencyHigh and catalytic effect, and is prepared by wet process.

The introduction of zinc carbonate coated zinc oxide inorganic filler with a wurtzite structure and a sphalerite structure which have central symmetry and non-axial symmetry can perform hydrogen bond complex reaction among molecules in a polyimide matrix to form valence chain molecules, inhibit the generation of interface defects among the molecules on the basis of larger energy band gap and exciton constraint energy of the zinc oxide inorganic filler, combine with various ligands to a great extent, form an integral body with polyamic acid and/or polyimide in the form of a complex or a chelate, eliminate the influence of internal reflection (refractive index difference matching among different material interfaces) generated between the interfaces of inorganic materials and organic materials, and greatly improve the optical properties of a colorless transparent polyimide film, such as light transmittance, haze and the like. Meanwhile, because polyimide has molecular chains with larger rigidity (amide bonds exist), the molecular chains are easy to generate orientation along the plane direction of the film, so that the refractive index nTE in the plane direction of the film is obviously larger than the refractive index nTM in the vertical direction, thereby causing the birefringence delta n of the film to be larger, introducing the nano zinc oxide inorganic filler coated with zinc carbonate through high-temperature pretreatment into the polyimide matrix, because the polyimide intermolecular and non-axisymmetric structure appearance and the nano zinc oxide particles with specific performance parameters generate synergistic effect, and on the basis that the zinc oxide filler coated with zinc carbonate has stronger catalytic action, the refractive index nTM in the vertical direction of the film is enhanced to a certain extent, the molecular chain orientation tends to be isotropic while the stacking density of the molecular chains is not weakened, so that the birefringence optical characteristics of the polyimide film can be reduced while the refractive index of the polyimide film is remarkably improved. Before coating, the nano zinc oxide is subjected to high-temperature oxygen removal pretreatment at the temperature of 300-1000 ℃ for 0.5-3.5 h, and for the nano zinc oxide, because the surface of the nano zinc oxide has adsorbed oxygen and hydroxyl oxygen, the amount of the oxygen existing in the two forms can change along with the change of time, such as the adsorption of moisture, the reabsorption and stripping of oxygen in the air and the like. The change of the quantity of oxygen in the two forms inevitably causes the change of molecular and electronic energy levels in the material, causes different light absorption, and the zinc carbonate layer is coated after the high-temperature oxygen removal pretreatment to facilitate the surface rarefaction of the zinc oxide inorganic filler, so that the refractive index and the birefringence of the film can be more effectively regulated and controlled, and the haze and other characteristics of the film can be further reduced.

In the same way, the applicant finds in a large number of experiments, research and analysis that the use of non-aromatic diamine, non-aromatic dianhydride and other polymerization monomers can not effectively improve the refractive index of the colorless transparent polyimide film and can not effectively reduce the birefringence optical characteristics of the colorless transparent polyimide film even if the nano zinc oxide inorganic filler with the surface coated with zinc carbonate is added into the polyamic acid or polyimide resin matrix. If a single non-aromatic diamine (a single diamine does not mean one kind of diamine, and can be a combination) or a single non-aromatic dianhydride (a single diamine does not mean one kind of diamine, and can be a combination) is selected as a polymerization monomer, the nano zinc oxide inorganic filler with the surface coated with zinc carbonate is introduced into the polyamide acid or the polyimide resin matrix under the same condition, and the effect of improving the optical properties of the colorless transparent polyimide film, such as refractive index, birefringence, and the like is limited.

The invention has the beneficial effects that:

1. in the existing inorganic nano hybrid transparent polyimide composite film, the polyimide and silicon dioxide network are easy to generate phase separation, so that the film is opaque, the light transmittance is poor, the mechanical property is greatly reduced, and even the film is difficult to form. By modifying it, for example, to prepare polyimide hybrid films having pendant hydroxyl, phenolic hydroxyl, or terminal siloxane groups, phase separation problems are improved but limited, particularly in the preparation of colorless transparent polyimide films. In addition, the polyimide/silicon dioxide hybrid material prepared by the sol-gel method can effectively improve the comprehensive properties of polyimide, such as heat resistance and mechanical properties, and reduce dielectric constant, thermal expansion coefficient, water absorption rate and the like. However, in the hybrid film, the polyimide and silicon dioxide network are easy to generate phase separation, so that the film is opaque, the light transmittance is poor, the mechanical property is greatly reduced, and even the film is difficult to form;

according to the invention, by selecting characteristic performance parameters and non-axisymmetric structural morphology nano zinc oxide, and coacting with a biaxial stretching forming process, the zinc oxide filler in the film is subjected to surface migration and creeping and uniform self-assembly to generate an irregularly formed modified surface; meanwhile, when nano zinc oxide particles are subjected to infrared heating radiation, photo-generated electrons and holes generated in the particles are quickly diffused to the surfaces of the particles to cause complex photochemical reaction on the surfaces, meanwhile, the zinc oxide particles can also generate a series of physical and chemical reactions under the action of light and heat in the environment of a polyimide matrix and an aprotic polar solvent, the potential problems of micro-phase and macro-phase separation and the like are eliminated under the condition of synergistic effect of various factors, the optical characteristics of the colorless transparent polyimide film, such as refractive index, birefringence and the like, are effectively regulated and controlled, and the compatibility and the dispersibility of the polyimide resin are the same as those of similarly selected amorphous silicon dioxide particles (free volume on the surface of a large filler, and aggregation of the silicon dioxide particles is prevented by mutual repulsive force of the amorphous silicon dioxide particles), so that the optical transparency (high light transmittance, high light transmittance and high light transmittance) of the polyimide are finally maintained, Low haze) so that the resulting polyimide film has superior mechanical properties, heat resistance, etc., and also has a low content of moisture and impurities, thereby exhibiting excellent optical characteristics.

2. By selecting the nano zinc oxide particle filler with non-axisymmetric structure appearance and specific performance parameters in the colorless transparent polyimide film, the obtained polyimide film has excellent mechanical properties, thermal properties (shrinkage rate, thermal expansion coefficient and the like) and insulating properties (electrical strength, dielectric constant and the like), and simultaneously further realizes controllable refractive index and lower birefringence parameters of the colorless transparent polyimide film, so that the requirements of the market can be met, and the application field of products can be enlarged.

3. The polyimide film prepared by the prior art has the light transmittance of more than 88.0 percent (wavelength of 550nm), the birefringence of less than 0.2, the haze of less than or equal to 1.0 percent, the refractive index of less than 1.65, the intrinsic surface hardness of 1.5-3.0H, the tensile strength of more than or equal to 180MPa, the elongation of more than 20 percent, the elastic modulus of more than 2.5GPa, and the Coefficient of Thermal Expansion (CTE) of less than or equal to 45 x 10^-6/° C, the shrinkage rate is less than or equal to 0.15 percent, and the Tg is more than 300 ℃;

the prepared colorless transparent polyimide film with the thickness of 2.5-150 mu mThe film has light transmittance of more than 90.0% (wavelength 550nm), birefringence of less than or equal to 0.02, haze of less than or equal to 0.2%, refractive index of 1.68-1.88, intrinsic surface hardness of more than 3.8H, tensile strength of more than or equal to 220MPa, elongation of more than 38%, elastic modulus of more than 5.0GPa, Coefficient of Thermal Expansion (CTE) of less than or equal to 20 × 10^-6/° c, shrinkage of not more than 0.05%, Tg > 350 ℃;

4. the method realizes controllable refractive index and low birefringence by adding the nano zinc oxide which is pretreated by heating and coated with the zinc carbonate, ensures continuous production, and has simple manufacturing process and convenient operation.

Detailed Description

The present invention will be described in detail with reference to the following examples.

Example 1

Preparation of polyamic acid resin solution

Adding 3.14kg of aromatic diamine 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (2,2' -TFDB) into 142.50kg of N, N ' -Dimethylacetamide (DMAC) solvent under the condition of controlling the temperature of a synthesis system to be 15 ℃ in a nitrogen atmosphere, stirring and dissolving, adding 4.36kg of aromatic dianhydride 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) with the molar ratio of 1:1 to the aromatic diamine into the mixture in 10 times at constant speed after the 2,2' -TFDB is completely dissolved, stirring the mixture at 1500r/min, and carrying out polycondensation reaction for 24 hours to obtain a polyamic acid resin solution with the solid content M of 7.50kg, namely the solid content ratio of 5 wt%;

II, preparation of nano zinc oxide slurry with surface coated with zinc carbonate

Coating zinc carbonate on the surface of zinc oxide with the particle size of 28nm and performing high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting the existing physical or chemical method to obtain a nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 3nm, adding the additive into N, N' -Dimethylformamide (DMAC) to sequentially perform 100r/min low-speed shearing stirring for 2h, 1000r/min high-speed shearing stirring pretreatment for 1h, 1400r/min emulsification treatment for 2h, 30MPa high-pressure homogenization treatment for 1h and 28khz ultrasonic dispersion treatment for 2h, wherein the weight of the additive is 28% of the weight of a polar aprotic solvent, and obtaining nano zinc oxide slurry with the surface coated with the zinc carbonate;

III, preparation of colorless transparent polyimide film

And (3) mixing and stirring the polyamic acid resin solution obtained in the step (I) and the nano zinc oxide slurry obtained in the step (II), wherein the amount of the nano zinc oxide slurry is 0.5 wt% of the solid content M in the polyamic acid resin solution obtained in the step (I), preparing a colorless transparent polyamic acid resin solution, defoaming for later use, coating the solution on an annular steel belt through an extrusion forming mold, wherein the thickness of the solution is 800 mu M, then enabling the annular steel belt to pass through an oven, and drying and curing at 100 ℃ to remove 20 wt% of solvent, thus obtaining the polyamic acid film with self-supporting property. The obtained polyamic acid film with self-supporting property is peeled off from an annular steel belt and is conveyed to a longitudinal and transverse biaxial stretcher for stretching by 1.2 times for 0.5h at the temperature of 150 ℃, imidization treatment is carried out for 0.1h at the temperature of 550 ℃, finally setting treatment is carried out for 7.5h at the temperature of 360 ℃, and the colorless transparent polyimide film with the thickness of 120 mu m is prepared by rolling.

Illustrative examples 2-6 differ from example 1 in the amount of nano-zinc oxide slurry, which was the same for all of the other examples

Example 2

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 0.8 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 3

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 1 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 4

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 5 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 5

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 12 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 6

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 18 wt% of the solid content M in the polyamic acid resin solution described in step I".

Examples 7 to 11 are different from example 1 in that the nano zinc oxide particles are different in size and the same in all other cases

Example 7

The difference between the embodiment and the embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 20nm and is subjected to high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 3 nm".

Example 8

The difference between the embodiment and the embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 25nm and is subjected to high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 3 nm".

Example 9

The difference between the embodiment and the embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 38nm and is subjected to high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 3 nm".

Example 10

The difference between the embodiment and the embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 80nm and is subjected to high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 3 nm".

Example 11

The difference between the embodiment and the embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 120nm and is subjected to high-temperature deoxidation pretreatment at 1000 ℃ for 0.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 3 nm".

Examples 12 to 14 differ from example 1 in that the zinc carbonate coating had a different thickness and was all the same

Example 12

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and is subjected to high temperature deoxidation pretreatment at 1000 ℃ for 0.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Example 13

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and is subjected to high temperature deoxidation pretreatment at 1000 ℃ for 0.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 15 nm".

Example 14

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and is subjected to high temperature deoxidation pretreatment at 1000 ℃ for 0.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 25 nm".

Example 15

Preparation of polyamic acid resin solution

Adding 46.7kg of aromatic diamine 3,3' -diamino-5, 5 ' -bis (trifluoromethyl) biphenyl (s-TFDB) into 230.40kg of N, N ' -Dimethylacetamide (DMAC) solvent under the condition of controlling the temperature of a synthesis system to be 35 ℃ in a nitrogen atmosphere, stirring and dissolving, after the s-TFDB is completely dissolved, adding 42.9kg of aromatic dianhydride 3,3',4,4' -biphenyl tetracarboxylic dianhydride (s-BPDA) with a molar ratio of 1:1 to the aromatic diamine at a constant speed for 8 times, stirring at 1000r/min, and carrying out polycondensation reaction for 18h to obtain a polyamic acid resin solution with a solid content M of 89.60kg, namely a solid content ratio of 28 wt%;

Coating zinc carbonate on the surface of zinc oxide with the particle size of 28nm and subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5 hours by adopting the existing physical or chemical method to obtain a nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 15nm, adding the additive into N, N' -Dimethylformamide (DMAC) to sequentially carry out 180r/min low-speed shearing and stirring for 8.5 hours, 1500r/min high-speed shearing and stirring pretreatment for 0.2 hour, 1800r/min emulsification treatment for 12 hours, 100MPa high-pressure homogenization treatment for 6 hours and 42khz ultrasonic dispersion treatment for 0.5 hour, wherein the weight of the additive is 5 wt% of the weight of a polar aprotic solvent, and obtaining nano zinc oxide slurry with the surface coated with the zinc carbonate;

III, preparation of colorless transparent polyimide film

And (3) mixing and stirring the polyamic acid resin solution obtained in the step (I) and the nano zinc oxide slurry obtained in the step (II), wherein the amount of the nano zinc oxide slurry is 0.5 wt% of the solid content M in the polyamic acid resin solution obtained in the step (I), preparing a colorless transparent polyamic acid resin solution, defoaming for later use, coating the solution on an annular steel belt through an extrusion forming mold, wherein the thickness of the solution is 400 mu M, then enabling the annular steel belt to pass through an oven, and drying and curing at 100 ℃ to remove 35 wt% of solvent, thus obtaining the polyamic acid film with self-supporting property. The obtained polyamic acid film with self-supporting property is peeled off from the annular steel belt and is conveyed to a longitudinal and transverse biaxial stretcher for stretching by 1.5 times at 180 ℃ for 1.5h, imidization treatment is carried out at 550 ℃ for 0.5h, finally setting treatment is carried out at 180 ℃ for 3.5h, and the colorless transparent polyimide film with the thickness of 80 mu m is prepared by rolling.

Examples 16-20 differ from example 15 in the amount of nano zinc oxide slurry and were all the same

Example 16

This example is different from example 15 in that "the amount of nano zinc oxide slurry is 0.8 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 17

This example is different from example 15 in that "the amount of nano zinc oxide slurry is 1 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 18

This example is different from example 15 in that "the amount of nano zinc oxide slurry is 5 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 19

This example is different from example 15 in that "the amount of nano zinc oxide paste is 12 wt% of the solid content M in the polyamic acid resin solution described in step I".

Example 20

This example differs from example 15 in that the amount of nano zinc oxide slurry is 18 wt% of the solid content M in the polyamic acid resin solution described in step I.

Examples 21 to 25 are different from example 15 in that the nano zinc oxide particles are different in size and the same in all other examples

Example 21

The difference between the embodiment and the embodiment 15 lies in that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 20nm and is subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 15 nm".

Example 22

The difference between the embodiment and the embodiment 15 lies in that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 25nm and is subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 15 nm".

Example 23

The difference between the embodiment and the embodiment 15 lies in that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 38nm and is subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5h by adopting a physical or chemical method, so as to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 15 nm".

Example 24

The difference between the embodiment and the embodiment 15 lies in that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 80nm and is subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 15 nm".

Example 25

The difference between the embodiment and the embodiment 15 lies in that "zinc carbonate is coated on the surface of zinc oxide with the particle size of 120nm and is subjected to high-temperature deoxidation pretreatment at 300 ℃ for 3.5h by adopting a physical or chemical method to obtain the nano zinc oxide additive with the surface coated with zinc carbonate and the thickness of 15 nm".

Examples 26 to 28 differ from example 15 in that the zinc carbonate coating was not of the same thickness, but was all of the same thickness

Example 26

The difference between the present embodiment and embodiment 15 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and subjected to high temperature deoxidation pretreatment at 300 ℃ for 3.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 3 nm".

Example 27

The difference between the present embodiment and embodiment 15 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and subjected to high temperature deoxidation pretreatment at 300 ℃ for 3.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Example 28

The difference between the present embodiment and embodiment 15 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and subjected to high temperature deoxidation pretreatment at 300 ℃ for 3.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 25 nm".

Examples 29 and 30 are control groups in which the amount of the nano zinc oxide inorganic filler powder whose surface is coated with zinc carbonate is out of the range defined in claim 1

Example 29

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 0.2 wt% of the solid content M in the polyamic acid resin solution described in step I, and a colorless transparent polyamic acid resin solution is prepared".

Example 30

This example is different from example 1 in that "the amount of nano zinc oxide slurry is 25 wt% of the solid content M in the polyamic acid resin solution described in step I, to obtain colorless transparent polyamic acid resin solution".

Examples 31 to 35 are control groups in which the nano-zinc oxide coating was not subjected to a high-temperature deoxidation pretreatment or the pretreatment temperature or time exceeded the range defined in claim 1

Example 31

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and without high-temperature deoxidation pretreatment by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 3 nm".

Example 32

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and subjected to high temperature deoxidation pretreatment at 1200 ℃ for 0.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Example 33

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and is subjected to high temperature deoxidation pretreatment at 100 ℃ for 0.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Example 34

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and is subjected to high temperature deoxidation pretreatment at 1000 ℃ for 0.2h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Example 35

The difference between the present embodiment and embodiment 1 is that "zinc carbonate is coated on the surface of zinc oxide with particle size of 28nm and subjected to high temperature deoxidation pretreatment at 1000 ℃ for 5.5h by using the existing physical or chemical method, so as to obtain the nano zinc oxide additive with surface coated zinc carbonate thickness of 6 nm".

Examples 36 and 37 are comparative examples in which the surface of the nano-zinc oxide inorganic filler powder was coated with zinc carbonate to a thickness outside the range defined in claim 1

Example 36

The difference between this example and example 1 is that "the thickness of the nano zinc oxide coated zinc carbonate is 2.6 nm".

Example 37

The difference between the present example and example 1 is that "the thickness of the nano zinc oxide coated zinc carbonate is 42 nm".

Example 38

Preparation of polyamic acid resin solution

Adding 32.54kg of diamine 3,3' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (3,3' -TFDB) and 5.09kg of diamine 3,4' -diaminodiphenyl ether (3,4' -ODA) into 225.0kg of N, N ' -Dimethylformamide (DMF) solvent under the nitrogen atmosphere and at the temperature of 22 ℃ of a synthesis system, stirring and dissolving, adding 37.37kg of dianhydride 2,3,3',4' -biphenyltetracarboxylic dianhydride (a-BPDA) with a molar ratio of 1:1 to the diamine into the mixture at a constant speed for 8 times after the HFBAPP and the 3,4' -ODA are completely dissolved, stirring the mixture at 1200r/min, and carrying out polycondensation reaction for 24 hours to obtain a polyamic acid resin solution with a solid content M of 75.0kg, namely a solid content ratio of 25 wt%;

Coating zinc carbonate on the surface of zinc oxide with the particle size of 38nm and subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2 hours by adopting the existing physical or chemical method to obtain a nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10nm, adding the additive into N, N' -Dimethylformamide (DMAC) to sequentially carry out 100r/min low-speed shearing and stirring for 8.5 hours, 1500r/min high-speed shearing and stirring pretreatment for 2 hours, 1000r/min emulsification treatment for 10 hours, 50MPa high-pressure homogenization treatment for 1.5 hours and 28khz ultrasonic dispersion treatment for 1.8 hours, wherein the weight of the additive is 15 wt% of the weight of a polar aprotic solvent, and obtaining nano zinc oxide slurry with the surface coated with the zinc carbonate; III, preparation of colorless transparent polyimide film

And (3) mixing and stirring the polyamic acid resin solution obtained in the step (I) and the nano zinc oxide slurry obtained in the step (II), wherein the amount of the nano zinc oxide slurry is 1.0 wt% of the solid content M in the polyamic acid resin solution obtained in the step (I), preparing a colorless transparent polyamic acid resin solution, defoaming for later use, coating the solution on an annular steel belt through an extrusion molding die, wherein the thickness of the solution is 360 mu M, then enabling the annular steel belt to pass through an oven, and drying and curing at 180 ℃ to remove 50 wt% of solvent, thus obtaining the polyamic acid film with self-supporting property. The obtained polyamic acid film with self-supporting property is peeled off from an annular steel belt and is conveyed to a longitudinal and transverse biaxial stretcher for stretching by 1.15 times at 165 ℃ for 2.5h, imidization treatment is carried out at 400 ℃ for 1.5h, finally setting treatment is carried out at 320 ℃ for 2.8h, and the colorless transparent polyimide film with the thickness of 38 mu m is prepared by rolling.

Examples 39 to 41 differ from example 38 in that the characteristic parameter conditions of the nano zinc oxide were optimized, all other things being equal

Example 39

The difference between the embodiment and the embodiment 38 lies in that "zinc oxide (with the specific surface area of 350 m) which is coated with zinc carbonate by the existing physical or chemical method and has the particle size of 38nm and is subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2h is adopted²(BET method test), pH 8.2, conductivity 550pS/cm, agglomeration index 45, refractive index 2.10]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 40

The difference between the embodiment and the embodiment 38 lies in that "zinc oxide (specific surface area 320 m) which is prepared by coating zinc carbonate with 38nm particle size and is subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2h by using the existing physical or chemical method²(BET method test), pH 8.0, conductivity 450pS/cm, agglomeration index 35, refractive index 2.05]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

EXAMPLE 41

The difference between the embodiment and the embodiment 38 lies in that "zinc oxide (the specific surface area is 300 m) which is prepared by coating zinc carbonate with 38nm particle size and is subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2h by adopting the existing physical or chemical method²(BET method test), pH 7.5, conductivity 350pS/cm, agglomeration index 25, refractive index 2.00]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 42

Preparation of polyamic acid resin solution

72.97kg of diamine 2, 2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane (HFBAPP) is added into 680kg of N, N '-Dimethylformamide (DMF) solvent under the nitrogen atmosphere and at the temperature of 22 ℃ to be stirred and dissolved, after the HFBAPP is completely dissolved, 31.26kg of dianhydride 3,4' -hexafluoroisopropyl phthalic anhydride (a-6FDA) and 15.77kg of dianhydride 1,2,4, 5-cyclohexane tetracarboxylic dianhydride (HPMDA) with the molar ratio of 1.1:1 to the diamine are added into the mixture at constant speed for 10 times, the mixture is stirred at 1200r/min, and the mixture is subjected to polycondensation reaction for 24 hours to obtain a polyamic acid resin solution with the solid content of 120kg, namely the solid content of 15 wt%;

Coating zinc carbonate on the surface of zinc oxide with the particle size of 80nm and subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2 hours by adopting the existing physical or chemical method to obtain a nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10nm, adding the additive into N, N' -Dimethylformamide (DMAC) to sequentially carry out 50r/min low-speed shearing and stirring for 8.5 hours, 500r/min high-speed shearing and stirring pretreatment for 1.8 hours, 1600r/min emulsification treatment for 1.8 hours, 60MPa high-pressure homogenization treatment for 1.5 hours and 42khz ultrasonic dispersion treatment for 2.2 hours, wherein the weight of the additive is 12 wt% of the weight of a polar aprotic solvent, and obtaining nano zinc oxide slurry with the surface coated with the zinc carbonate;

III, preparation of colorless transparent polyimide film

And (3) mixing and stirring the polyamic acid resin solution obtained in the step (I) and the nano zinc oxide slurry obtained in the step (II), wherein the amount of the nano zinc oxide slurry is 1.0 wt% of the solid content M in the polyamic acid resin solution obtained in the step (I), preparing a colorless transparent polyamic acid resin solution, defoaming for later use, coating the solution on an annular steel belt through an extrusion forming mold, wherein the thickness of the solution is 100 mu M, then enabling the annular steel belt to pass through an oven, and drying and curing at 250 ℃ to remove 20 wt% of solvent, thus obtaining the polyamic acid film with self-supporting property. The obtained polyamic acid film with self-supporting property is peeled off from an annular steel belt and is conveyed to a longitudinal and transverse biaxial stretcher for 0.9 time stretching for 5.5h at 178 ℃, imidization treatment is carried out for 8.8h at 450 ℃, finally setting treatment is carried out for 0.1h at 200 ℃, and a colorless transparent polyimide film with the thickness of 18 mu m is prepared by rolling.

Examples 43 to 45 differ from example 42 in that the characteristic parameter conditions of the nano-zinc oxide were optimized, all else being equal

Example 43

The difference between the present example and example 42 is that "zinc oxide with particle size of 38nm and high temperature deoxidation pretreatment at 800 ℃ for 2.2h is coated with zinc carbonate by existing physical or chemical method [ specific surface area 48m²(BET method test), pH 5.8, conductivity 550pS/cm, agglomeration index 42, refractive index 1.90]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 44

The difference between the present example and example 42 is that "zinc oxide with particle size of 38nm and high temperature deoxidation pretreatment at 800 ℃ for 2.2h is coated with zinc carbonate by existing physical or chemical method [ specific surface area 100m²(BET method test), pH 6.2, conductivity 450pS/cm, agglomeration index 32, refractive index 1.95]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 45

The difference between the present example and example 42 is that "zinc oxide with particle size of 38nm and high temperature deoxidation pretreatment at 800 deg.C for 2.2h is coated with zinc carbonate by existing physical or chemical method [ specific surface area 180m²(BET method test), pH 6.5, conductivity 350pS/cm, agglomeration index 22, refractive index 1.98]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 46

Preparation of polyamic acid resin solution

Under nitrogen atmosphere, controlling the temperature of a synthesis system to be 22 ℃, adding 17.70kg of diamine 2, 2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane (HFBAPP) and 4.56kg of diamine 3,4' -diaminodiphenyl ether (3,4' -ODA) into 84kg of N, N ' -Dimethylformamide (DMF) solvent, stirring and dissolving, after the HFBAPP and the 3,4' -ODA are completely dissolved, adding 11.231kg of dianhydride 4,4' -oxydiphthalic anhydride (ODPA) and 3.883kg of dianhydride 1,2,4, 5-cyclohexane tetracarboxylic dianhydride (HPMDA) with a molar ratio of 1.1:1 into the mixture at constant speed for 5 times, stirring the mixture at 1000r/min, and carrying out polycondensation reaction for 24 hours to obtain a polyamic acid resin solution with a solid content of M of 37.37kg, namely a solid content of 30.8 wt%;

Coating zinc carbonate on the surface of zinc oxide with the particle size of 38nm and subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2 hours by adopting the existing physical or chemical method to obtain a nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10nm, adding the additive into N, N' -Dimethylformamide (DMAC) to sequentially carry out 80r/min low-speed shearing stirring for 8.5 hours, 1500r/min high-speed shearing stirring pretreatment for 0.8 hour, 800r/min emulsification treatment for 10 hours, 80MPa high-pressure homogenization treatment for 5 hours and 42khz ultrasonic dispersion treatment for 1.2 hours, wherein the weight of the additive is 20 wt% of the weight of a polar aprotic solvent, and obtaining nano zinc oxide slurry with the surface coated with the zinc carbonate;

III, preparation of colorless transparent polyimide film

And (3) mixing and stirring the polyamic acid resin solution obtained in the step (I) and the nano zinc oxide slurry obtained in the step (II), wherein the amount of the nano zinc oxide slurry is 1.0 wt% of the solid content M in the polyamic acid resin solution obtained in the step (I), preparing a colorless transparent polyamic acid resin solution, defoaming for later use, coating the solution on an annular steel belt through an extrusion forming mold, wherein the thickness of the solution is 200 mu M, then passing the annular steel belt through an oven, and drying and curing at 120 ℃ to remove 30 wt% of solvent, thereby obtaining the polyamic acid film with self-supporting property. The obtained polyamic acid film with self-supporting property is peeled off from an annular steel belt and is conveyed to a longitudinal and transverse biaxial stretcher for stretching by 1.1 times for 2.5h at 165 ℃, imidization treatment is carried out for 3.5h at 500 ℃, finally setting treatment is carried out for 5.5h at 300 ℃, and a colorless transparent polyimide film with the thickness of 50 mu m is prepared by rolling.

Examples 47 to 49 differ from example 46 in that the characteristic parameter conditions of the nano zinc oxide were optimized, all else being equal

Example 47

The difference between the embodiment and the embodiment 46 lies in that the zinc oxide (the specific surface area is 200 m) which has the particle size of 38nm and is subjected to high-temperature deoxidation pretreatment at 800 ℃ for 2.2h is coated with zinc carbonate by adopting the existing physical or chemical method²(BET method test), pH 7.2, conductivity 300pS/cm, agglomeration index 38, refractive index 1.98]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 48

The difference between the present example and example 46 is that "zinc oxide with particle size of 38nm and high temperature deoxidation pretreatment at 800 deg.C for 2.2h is coated with zinc carbonate by existing physical or chemical method [ specific surface area 240m²(BET method test), pH 7.2, conductivity 250pS/cm, agglomeration index 28, refractive index 1.95]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 49

The difference between the embodiment and the embodiment 46 lies in that the zinc oxide (the specific surface area is 280 m) which is coated with the zinc carbonate by the existing physical or chemical method and has the particle size of 38nm and is subjected to the high-temperature deoxidation pretreatment at 800 ℃ for 2.2h²(BET method test), pH 7.2, conductivity 200pS/cm, agglomeration index 18, refractive index 1.99]And (5) obtaining the nano zinc oxide additive with the surface coated with the zinc carbonate and the thickness of 10 nm.

Example 50

The difference between this example and example 1 is that "the step of blending and stirring the polyamic acid resin solution and the nano zinc oxide slurry is eliminated, and finally the colorless transparent polyimide film without zinc oxide is obtained". This example is a control group.

Example 51

The difference between this example and example 15 is that "the step of blending and stirring the polyamic acid resin solution and the nano zinc oxide slurry is eliminated, and finally the colorless transparent polyimide film without zinc oxide is obtained". This example is a control group.

Example 52

The difference between this example and example 38 is that "the step of blending and stirring the polyamic acid resin solution and the nano zinc oxide slurry is eliminated, and finally the colorless transparent polyimide film without zinc oxide is obtained". This example is a control group.

Example 53

The difference between this example and example 42 is that "the step of blending and stirring the polyamic acid resin solution and the nano zinc oxide slurry is eliminated, and finally the colorless transparent polyimide film without zinc oxide is obtained". This example is a control group.

Example 54

The difference between this example and example 46 is that "the step of blending and stirring the polyamic acid resin solution and the nano zinc oxide slurry is eliminated, and finally the colorless transparent polyimide film without zinc oxide is obtained". This example is a control group.

Results and discussion

TABLE 1

TABLE 2

TABLE 3

As shown in tables 1 and 2, the colorless and transparent polyimide films prepared in examples 1 to 28 have relatively high light transmittance, refractive index controlled between 1.68 and 1.88 according to the defined filler, low birefringence (reduced by orders of magnitude), haze (reduced by orders of magnitude), and other excellent optical properties, and also exhibit high mechanical properties (e.g., high intrinsic surface hardness, high tensile strength, high elongation, high modulus) and good thermal properties (e.g., low CTE, low shrinkage, high Tg); in addition, in the embodiments 2-5, 16-19, especially 3-4, 17-18, the addition amount of the zinc oxide inorganic filler coated with zinc carbonate is in a specific range, so that the optical property of the film is better, and the thermal property and the mechanical property of the film are better; also in examples 7-11, 12-14, 21-25, 26-28, especially 7-10, 12-13, 21-24, 26-27, the inorganic filler is zinc oxide with different particle sizes and zinc carbonate coating thickness in a specific range, and the obtained colorless transparent polyimide film has better optical properties, thermal properties and mechanical properties. As shown in table 3, the colorless transparent polyimide films prepared in examples 38 to 49 by changing the types of the polymerized monomers and performing multiple polymerization also have relatively high light transmittance, the refractive index thereof can be controlled between 1.68 and 1.88, and the films have excellent optical properties such as low birefringence (reduced by orders of magnitude), haze (reduced by orders of magnitude), and the like, and also show high mechanical properties (such as high tensile strength, high elongation, modulus) and good thermal properties (such as low CTE, low shrinkage, high Tg); and the colorless transparent polyimide film prepared by using zinc oxide satisfying the characteristic parameters is further superior in the examples 39 to 41, 43 to 45, and 47 to 49, particularly in the examples 40, 44, and 48 in combination.

On the other hand, the colorless transparent polyimide films prepared in comparative examples 50-54, which did not use zinc oxide inorganic filler pre-treated by high temperature deoxidation and coated with zinc carbonate, as shown in tables 1,2, 3, did not have the desired optical properties (lower light transmittance, birefringence, refractive index, etc.), thermal properties (lower Tg, higher CTE, shrinkage, etc.), and mechanical properties (lower intrinsic surface hardness, lower modulus, tensile strength, elongation, etc.). In comparative examples 29 to 37, the zinc oxide inorganic filler used in the method is not subjected to high temperature deoxidation pretreatment or the technical parameters such as the addition amount, the particle size, the coating thickness of the zinc oxide inorganic filler are out of the range defined in claim 1 or the temperature and time of the high temperature deoxidation pretreatment before the zinc oxide inorganic filler is coated are out of the range defined in claim 1, and the prepared colorless transparent polyimide film has relatively poor optical properties, thermal properties and mechanical properties.

The reason may be that the nano zinc oxide has small particle size and is easy to agglomerate or the film has large haze due to large particle size; or the optical properties such as refractive index, birefringence and the like cannot be effectively regulated when the addition amount is too small, or the comprehensive performance of the film is deteriorated due to dispersion unevenness caused by too large addition amount; in addition, the temperature and time of high-temperature deoxidation pretreatment before coating or zinc carbonate coating are not in a limited range, which can cause incomplete treatment of adsorbed oxygen and hydroxyl oxygen on the surface of a zinc oxide material, further cause the change of molecular and electronic energy levels in the material, cause different light absorption, and directly influence the optical properties of the filler regulation film, such as refractive index, birefringence, haze and the like.

The parameters in tables 1,2 and 3 were measured as follows. The mechanical properties of the colorless transparent polyimide film are as described in GB/T13542.2-2009 part 2 of film for electrical insulation: test method "; the intrinsic surface hardness film hardness test (pencil method) was performed according to ASTM D3363 test method; shrinkage (dimensional stability) according to GB/T13542.2-2009 part 2 of film for electrical insulation: test methods test (200 ℃); the transmission was measured according to ISO14782:1999 and the haze was measured according to ASTM D1003-6; glass transition temperature (Tg), coefficient of thermal linear expansion (CTE), respectively adopting a differential scanning calorimeter and a thermal mechanical analyzer to test in a nitrogen atmosphere, wherein the testing temperature range of the CTE is 100-300 ℃; the light transmittance (T500) and the haze at the wavelength of 500nm are tested by an ultraviolet-visible spectrometer; refractive index, birefringence, etc. were measured using a Prism Coupler of waveguide Prism type-SPA-4000, manufactured by Sairon Tech of Korea, nTE being in-plane refractive index, nTM being out-of-plane refractive index, nav being average refractive index, birefringence Δ n being nTE-nTM, and a measurement wavelength of 632.8 nm. Ultraviolet-visible (UV-Vis) spectrophotometer (test wavelength range is 200-800 nm), UV-3600 model, Shimadzu corporation, Japan; a light transmittance/haze meter, WGT-S model, denland opto-electro-mechanical technologies ltd; an electronic universal tensile machine, a KD111-0.2 model, Kaiqian testing instrument Limited of Shenzhen; a two-dimensional optical image measuring instrument, Easson EV-4030, Ningbo Yixin opto-electronic technology, Inc.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The colorless transparent polyimide film with the adjustable refractive index is characterized by comprising a polyimide body, wherein an additive is uniformly dispersed in the polyimide body, and the additive is nano zinc oxide with the surface coated with zinc carbonate;

2. The refractive index-controllable colorless transparent polyimide film according to claim 1, wherein the specific surface area of the nano zinc oxide is 48-350m²The pH value is 5.8-8.2, the conductivity is less than 600pS/cm, the agglomeration index is less than or equal to 50, and the refractive index is 1.9-2.1.

3. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the nano zinc oxide has a particle size of 25-80 nm.

4. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the nano zinc oxide has a particle size of 28-38 nm.

5. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the nano zinc oxide is wurtzite structure or sphalerite structure with central symmetry and non-axial symmetry.

6. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the coating thickness of the zinc carbonate is 6-15 nm.

7. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the additive is present in an amount of 0.8 wt% to 12 wt% based on the total weight of the polyimide film.

8. The refractive index controllable colorless transparent polyimide film according to claim 1, wherein the weight of the additive is 1-5 wt% of the total weight of the polyimide film.

9. A method for producing a polyimide film according to any one of claims 1 to 8, comprising the steps of:

10. The method for preparing a polyimide film according to claim 9, wherein the polyamic acid resin is prepared by reacting an aromatic diamine and an aromatic dianhydride in a molar ratio (0.9-1.1): 1 is uniformly dispersed in the polar aprotic solvent and stirred for reaction for 2-24h at the speed of 100-1500r/min to obtain polyamic acid resin;

11. The method for producing a polyimide film according to claim 9, wherein the aromatic diamine is selected from the group consisting of 3,4' -diaminodiphenyl ether (3,4' -ODA), 4' -diaminodiphenyl ether (4,4' -ODA), 2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (2,2' -TFDB), 3' -bis (trifluoromethyl) -4,4' -diaminobiphenyl (3,3' -TFDB), 4' -diaminobiphenyl, m-phenylenediamine (m-PDA), p-phenylenediamine (p-PDA), 2' -bistrifluoromethyl-4, 4' -diaminodiphenyl ether (TFODA), 3' -diamino-5, 5 ' -bistrifluoromethylbiphenyl (s-TFDB), 2, 2-bis (trifluoromethyl) -4,4 '-diaminophenylsulfone (SFTA), 4' -bis (2-trifluoromethyl-4-aminophenoxy) diphenylsulfone, 2- (4-aminophenyl) -5-aminobenzimidazole (APBIA), 4 '-bis (3-aminophenoxy) diphenylsulfone (M-BAPS), bis (3-aminophenyl) sulfone (3-DDS), bis (4-aminophenyl) sulfone (4-DDS), 4' -bis (4-aminophenoxy) biphenyl (BAPB), 1, 3-bis (3-aminophenoxy) benzene (TPE-M), 1, 3-bis (4-aminophenoxy) benzene (TPE-R), 1, 4-bis (4-aminophenoxy) benzene (TPE-Q), Any one or a combination of any more of 2,2' -bis [4- (4-aminophenoxy phenyl) ] propane (BAPP), 2-bis [4- (4-aminophenoxy) phenyl ] Hexafluoropropane (HFBAPP), 9-bis (3-fluoro-4-aminophenyl) fluorene (FFDA), 9-bis (3-methyl-4-aminophenyl) fluorene (BMAPF), 9-bis (4-aminophenyl) Fluorene (FDA);

12. The method for producing a polyimide film according to claim 9, wherein the amounts of the aromatic diamine, the aromatic dianhydride and the polar aprotic solvent are controlled so that the ratio of the solid content M in the polyamic acid resin solution formed in the present step is 5 to 60 wt%.

13. The method for preparing polyimide film according to claim 9, further comprising, before blending, subjecting the additive to the following treatment,

14. The method of preparing a polyimide film according to claim 10 or 13, wherein the polar aprotic solvent is selected from any one of low molecular weight carboxyamides, specifically N, N '-Dimethylacetamide (DMAC), N' -Dimethylformamide (DMF), N-methylpyrrolidone (NMP), Dimethylsulfoxide (DMSO), tetramethylsulfoxide, N '-dimethyl-N, N' -propyleneurea (DMPU), cyclopentanone, cyclohexanone, dichloromethane, monochlorobenzene, dichlorobenzene, chloroform, tetrahydrofuran, 3-methyl-N, N-dimethylpropionamide, N-dialkylcarboxyamide, m-cresol, γ -butyrolactone, or a combination of any more thereof.