CN111704735B - Polyimide optical film material with ultralow thermal expansion coefficient and high strength and preparation method thereof - Google Patents

Abstract

The invention discloses a polyimide optical film material with ultralow thermal expansion coefficient and high strength and a preparation method thereof, wherein the polyimide optical film material is prepared by performing polycondensation reaction on an aromatic dianhydride monomer, an aromatic diamine monomer containing an amide bond and a diamine monomer without an amide bond to form polyamic acid glue solution, performing spin coating to form a film and performing thermal imidization; the invention also discloses a preparation method of the material, the preparation method is simple, and the prepared polyimide film has ultralow thermal expansion coefficient, high mechanical strength, good optical permeability and good thermal stability; the polyimide film material is obtained by a spinning method, can be applied to the fields of optical film diffraction lenses, flexible film solar cells, OLED flexible display substrates and the like, and has wide application prospects.

Description

Polyimide optical film material with ultralow thermal expansion coefficient and high strength and preparation method thereof

Technical Field

The invention belongs to the field of materials, and particularly relates to an ultralow-thermal-expansion-coefficient high-strength polyimide optical film material and a preparation method thereof.

Background

Polyimide is a high-performance polycondensate with imide ring on the main chain, and is widely applied to the fields of aerospace, electronic industry, screen display and the like due to high mechanical strength, resistance, chemical corrosion resistance and excellent thermal stability.

However, the traditional polyimide film material has poor thermal dimensional stability and large dimensional change due to environmental temperature change, which severely limits the application of the polyimide film material in the photoelectric field. Polyimide films with high dimensional stability have several urgent needs, such as replacement of conventional inorganic materials as a base material for thin film optical elements in lightweight imaging systems; a flexible substrate as a new generation display screen; as a flexible substrate for solar cells.

Therefore, a polyimide film material having high dimensional stability, high strength and high thermal stability is highly demanded, and is a new generation of base material in lightweight optical systems, flexible displays and solar cell technologies.

Disclosure of Invention

In order to solve the above technical problems, one of the purposes of the present invention is to provide a polyimide optical film material with high thermal dimensional stability and high strength: the second object of the invention is to provide a preparation method of polyimide optical film material with high thermal dimensional stability and high strength, wherein the thermal expansion coefficient of the prepared polyimide film is-2 ppm-5 ppm/. Degree.C at-150-100 ℃; the tensile strength is 200-250 MPa; the glass transition temperature is 280-380 ℃; the average transmittance is 70-80% at 500-800 nm.

In order to achieve the above purpose, the present invention provides the following technical solutions: an ultralow thermal expansion coefficient high-strength polyimide optical film material, which is prepared from aromatic diamine and aromatic dianhydride monomers in a molar ratio of 1: (0.98-1.02) to form polyamic acid glue solution, adding chain segment end capping agent to control the chain segment molecular weight, spinning to form film, and thermal imidizing.

In the invention, the initial stage of the polycondensation reaction is required to be carried out at a lower temperature, the reaction temperature is selected to be 0-25 ℃, and the polycondensation time is 24-48 hours.

According to the invention, the end capping agent is added after the polycondensation reaction is finished to control the viscosity (molecular weight) of the glue solution, so that the mechanical property of the film after film formation can be effectively controlled, and the optical uniformity of the film after film formation can be facilitated after subsequent spin coating. The end-capping agent can be isophthalic acid, acetylene, 3- (3-phenylacetylphenyl), norbornyl anhydride, maleimide and allyl norbornyl.

In the invention, the aromatic dianhydride is one or a mixture of more of BPDA and PMDA;

the diamine is one or a mixture of more than one of diamine DABA and TMDB containing amide bonds;

the thermal expansion coefficient of the polyimide optical film material is-2 ppm-5 ppm/. Degree.C at-150-100 ℃; the tensile strength is 200-250 MPa; the glass transition temperature is 280-380 ℃; the average transmittance is 70-80% at 500-800 nm.

The invention also provides a preparation method of the polyimide optical film material, which comprises the following steps: dispersing diamine monomer containing amide bond in polar aprotic solvent under nitrogen protection, stirring and dissolving, adding dianhydride monomer in batches, wherein the molar ratio of the diamine monomer to the dianhydride monomer is 1: (0.98-1.02), adding a blocking agent to control the molecular weight of the glue solution after the reaction is finished, wherein the solid content of the polyamic acid glue solution is 7-10%, and stirring for 24-48 hours at 0-25 ℃ to obtain the polyamic acid solution.

Preferably selecting glue solution, filtering to remove bubbles, and finally spinning the polyamic acid glue solution on a quartz substrate with good surface shape to form a film, and removing the base material through thermal imidization to obtain the polyimide optical film material with good comprehensive performance

The polar aprotic solvent is any one or a plurality of mixed solvents mixed in any proportion of N-methylpyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide.

The invention has the following effective effects: the polyimide optical film material with ultralow thermal expansion coefficient and high strength has ultralow thermal expansion coefficient, high mechanical strength, high heat resistance and high transmittance, and the thermal expansion coefficient of-150-100 ℃ is-2 ppm-5 ppm/DEGC; the tensile strength is 200-250 MPa; the glass transition temperature is 280-380 ℃; the average transmittance is 70-80% at 500-800 nm, can be applied to the fields of optical thin film diffraction lenses, flexible thin film solar cells, OLED flexible display substrates and the like, and has wide application prospects.

Drawings

In order to make the objects, technical solutions and advantageous effects of the present invention clearer, the present invention provides the following drawings:

FIG. 1 is a graph showing the results of a test for the change in the thermal expansion dimensions of a polyimide film in the PMDA/BPDA-TMDB system of example 1, and the thermal expansion coefficient at-150 to 100deg.C is-0.95 ppm/deg.C.

FIG. 2 is a graph of the results of five tests on the tensile strength of polyimide films in the PMDA/BPDA-TMDB system of example 1, calculated to have an average tensile strength of 250MPa.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The test methods without specific conditions noted in the examples are generally conducted under conventional conditions or under conditions recommended by the manufacturer.

Example 1

Introducing nitrogen into a three-neck round-bottom flask with 500ml of a stirrer, adding 0.050mol of TMDB, dissolving in 240g of N, N-dimethylacetamide, then respectively adding 0.0245mol of PMDA and 0.0245mol of BPDA, keeping the reaction temperature at 0 ℃, continuously stirring and reacting for 30min, reacting at room temperature for 24-48 h, adding an end-capping agent isophthalic acid after the reaction is finished, continuously stirring for 30min to obtain a polyamic acid glue solution with the solid content of 10.0%, pressurizing and filtering the obtained glue solution, and removing bubbles from the obtained polyamic acid glue solution in vacuum; and (3) spinning a polyamide acid glue solution wet film with a certain thickness on a quartz substrate by using a spin coater, performing heating plate pre-baking treatment, then baking in a vacuum oven at 100 ℃ for 1 hour, baking at 200 ℃ for 1 hour, baking at 350 ℃ for 1 hour, and removing the film after the thermal imidization process is completed to obtain a uniform film with the thickness of 25 mu m. The resulting film was subjected to thermal expansion coefficient and tensile strength test, and the results are shown in FIGS. 1 and 2.

Example 2

Introducing nitrogen into a three-neck round-bottom flask with 500ml of a stirrer, adding 0.050mol of DABA, dissolving in 240g N-methylpyrrolidone, then respectively adding 0.025mol of PMDA and 0.025mol of BPDA, keeping the reaction temperature at 0 ℃, continuously stirring and reacting for 30min, reacting at room temperature for 24-48 h, adding an end-capping agent isophthalic acid after the reaction is finished, continuously stirring for 30min to obtain a polyamic acid glue solution with the solid content of 10.0%, pressurizing and filtering the obtained glue solution, and removing bubbles of the obtained polyamic acid glue solution in vacuum; and (3) spinning a polyamide acid glue solution wet film with a certain thickness on a quartz substrate by using a spin coater, performing heating plate pre-drying treatment, then baking for 1 hour at 100 ℃ in a vacuum oven through temperature programming, baking for 1 hour at 200 ℃ and baking for 1 hour at 350 ℃, and removing the film after the thermal imidization process is finished to obtain a uniform film with the thickness of 20 mu m. The resulting films were tested for coefficient of thermal expansion, tensile strength and similar to those of FIGS. 1 and 2.

Example 3

Introducing nitrogen into a three-neck round-bottom flask with 500ml of a stirrer, adding 0.040mol of TMDB, dissolving in 240g of N, N-dimethylacetamide, then respectively adding 0.041mol of BPDA, keeping the reaction temperature at 0 ℃, continuously stirring for reaction for 30min, reacting at room temperature for 24-48 h, adding an end-capping agent isophthalic acid after the reaction is completed, continuously stirring for 30min to obtain polyamic acid glue solution with the solid content of 8.0%, pressurizing and filtering the obtained glue solution, and removing bubbles in vacuum from the obtained polyamic acid glue solution; and (3) spinning a polyamide acid glue solution wet film with a certain thickness on a quartz substrate by using a spin coater, performing heating plate pre-drying treatment, then baking for 1 hour at 100 ℃ in a vacuum oven through temperature programming, baking for 1 hour at 200 ℃ and baking for 1 hour at 350 ℃, and removing the film after the thermal imidization process is finished to obtain a uniform film with the thickness of 20 mu m. The resulting films were tested for coefficient of thermal expansion, tensile strength and similar to those of FIGS. 1 and 2.

Example 4

Introducing nitrogen into a three-neck round bottom flask with 500ml of a stirrer, adding 0.020mol of TMDB and 0.020mol of DABA, dissolving in 240g N-methylpyrrolidone, then respectively adding 0.0205mol of BPDA and 0.0205mol of PMDA, keeping the reaction temperature at 0 ℃, continuously stirring for reacting for 60min, reacting for 24-48 h at room temperature, adding a blocking agent 3- (3-phenylacetylphenol group) after the reaction is finished, continuously stirring for 30min to obtain polyamic acid glue solution with the solid content of 8.0%, pressurizing and filtering the obtained glue solution, and removing bubbles from the obtained polyamic acid glue solution in vacuum; and (3) spinning a polyamide acid glue solution wet film with a certain thickness on a quartz substrate by using a spin coater, performing heating plate pre-baking treatment, then baking in a vacuum oven at 100 ℃ for 1 hour, baking at 200 ℃ for 1 hour, baking at 350 ℃ for 1 hour, and demolding after the thermal imidization process is completed to obtain a uniform film with the thickness of 15 mu m. The resulting films were tested for coefficient of thermal expansion, tensile strength and similar to those of FIGS. 1 and 2.

Example 5

Introducing nitrogen into a three-neck round-bottom flask with 500ml of a stirrer, adding 0.0175mol TMDB and 0.0175mol DABA, dissolving in 240g N, N-dimethylformamide, then respectively adding 0.0357mol BPDA, keeping the reaction temperature at 0 ℃, continuously stirring for reaction for 30min, reacting at room temperature for 24-48 h, adding a blocking agent norbornyl anhydride after the reaction is finished, continuously stirring for 30min to obtain a polyamic acid glue solution with 7.0% of solid content, pressurizing and filtering the obtained glue solution, and removing bubbles of the obtained polyamic acid glue solution in vacuum; and (3) spinning a polyamide acid glue solution wet film with a certain thickness on a quartz substrate by using a spin coater, performing heating plate pre-baking treatment, then baking in a vacuum oven at 100 ℃ for 1 hour, baking at 200 ℃ for 1 hour, baking at 300 ℃ for 1 hour, and demoulding after the thermal imidization process is finished to obtain a uniform film with the thickness of 28 mu m. The resulting films were tested for coefficient of thermal expansion, tensile strength and similar to those of FIGS. 1 and 2.

TABLE 1 polyimide optical film Performance test

	Tensile Strength (MPa)	CTE(ppm/℃)	Tg(℃)	500-800 nm transmittance (%)
					Example 1	250	0.9	380	80
Example 2	245	-2	350	77
					Example 3	200	5	330	72
Example 4	220	3	280	73
					Example 5	210	1.5	300	79

The result shows that the thermal expansion coefficient of the polyimide optical film material is-2 ppm-5 ppm/. Degree.C at-150-100 ℃; the tensile strength is 200-250 MPa; the glass transition temperature is 280-380 ℃; the average transmittance is 70-80% at 500-800 nm.

Finally, it is noted that the above-mentioned preferred embodiments are only intended to illustrate rather than limit the invention, and that, although the invention has been described in detail by means of the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims (1)

1. An ultra-low thermal expansion coefficient high strength polyimide optical film material is characterized in that: the polyimide optical film material is prepared from aromatic diamine and aromatic dianhydride monomers in a molar ratio of 1: (0.98-1.02) performing polycondensation reaction to form polyamic acid glue solution, adding a chain segment end capping agent to control the chain segment molecular weight after reaching a certain molecular weight, and performing spinning film formation and thermal imidization to obtain the polyamide resin;

the aromatic dianhydride is one or two of 3,3', 4' -biphenyl tetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA); the aromatic diamine is 4,4' -Diaminobenzidine (DABA) containing an amide bond and 2,2' -dimethyl-4, 4' -diaminobiphenyl (TMDB) without an amide bond; the end capping agent is isophthalic acid;

the thermal expansion coefficient of the polyimide optical film material is-2 ppm-5 ppm/. Degree.C at-150-100 ℃; the tensile strength is 200-250 MPa; the glass transition temperature is 280-380 ℃; the average transmittance is 70-80% at 500-800 nm;

the preparation method of the polyimide optical film material with ultralow thermal expansion coefficient and high strength comprises the following steps: dispersing diamine monomer containing amide bond in polar aprotic solvent under nitrogen protection, stirring and dissolving, adding dianhydride monomer in batches, wherein the molar ratio of the diamine monomer to the dianhydride monomer is 1: (0.98-1.02), adding a blocking agent to control the molecular weight of the glue solution after the reaction is finished, wherein the solid content of the polyamic acid glue solution is 7-10%, stirring for 24-48 hours at the temperature of 0-25 ℃ to obtain a polyamic acid solution, spin-coating the polyamic acid glue solution on a quartz substrate with good surface quality to form a film, and performing thermal imidization and substrate removal to obtain a polyimide optical film material with good comprehensive performance;

the temperature of the polycondensation reaction is 0-25 ℃, and the polycondensation reaction time is 24-48 hours;

the polar aprotic solvent is any one or a plurality of mixed solvents mixed in any proportion of N-methylpyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide.

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