1. A preparation method of a matte insulating polyimide black film is characterized by comprising the following steps:

s1, reacting aromatic dianhydride with aromatic diamine with molar quantity being excessive relative to the aromatic dianhydride in an aprotic polar solvent under inert atmosphere to obtain polyamide acid solution with excessive amine;

s2, adding silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, uniformly dispersing, and adding aromatic dianhydride for reaction to obtain polyamide acid mixed solution;

s3, forming and imidizing the polyamic acid mixed solution to obtain a matte insulating polyimide black film;

the total molar amount of the aromatic dianhydride added in steps S1 and S2 is equal to the molar amount of the aromatic diamine added in step S1.

2. The method for preparing the matte insulated polyimide black film according to claim 1, wherein the average particle size of the silane coupling agent modified polyimide powder is 3-5 μm.

3. The method for preparing the matte insulated polyimide black film according to claim 1 or 2, wherein the mass of the silane coupling agent modified polyimide powder is 3-5% of the sum of the mass of the aromatic dianhydride added in step S1 and the mass of the aromatic diamine added in step S1.

4. The method for preparing the matte insulated polyimide black film according to any one of claims 1 to 3, wherein the method for preparing the silane coupling agent modified polyimide powder comprises the following steps:

(a) in an inert atmosphere, stirring and reacting aromatic diamine and aromatic dianhydride with molar weight being excessive relative to the aromatic diamine in an aprotic polar solvent at 20-30 ℃ for 1-3 h to obtain polyamide acid solution with solid content being 1-5% wt and excessive anhydride;

(b) and adding an aminosilane coupling agent into the polyamide acid solution with excessive anhydride, stirring and reacting for 8-12 h at the temperature of 60-80 ℃, then adding a dehydrating agent and a catalyst, stirring and reacting for 8-12 h at the temperature of 80-100 ℃ to perform chemical imidization, after the reaction is finished, keeping the temperature of a reaction system at the temperature of 130-150 ℃ for 6-10 h, cooling, filtering, and washing, drying and crushing the obtained solid substance to obtain the polyamide acid.

5. The method for preparing a matte insulated polyimide black film according to claim 4, wherein in the method for preparing the silane coupling agent modified polyimide powder, the molar ratio of the aromatic diamine to the aromatic dianhydride to the aminosilane coupling agent to the dehydrating agent to the catalyst is 1 (1.05-1.2) to (0.2-0.3) to (2-3) to (1.5-2.5).

6. The preparation method of the matte insulating polyimide black film according to any one of claims 1 to 5, wherein the solid content of the carbon black color paste is 8-12 wt%, and D is₅₀＜300nm。

7. The method for preparing the matte insulated polyimide black film according to any one of claims 1 to 6, wherein the mass of the carbon black color paste is 6 to 9 percent of the mass of the amine-excessive polyamic acid solution.

8. The method for preparing the matte insulating polyimide black film according to any one of claims 1 to 7, wherein in the step S1, the molar ratio of the aromatic dianhydride to the aromatic diamine is (0.97-0.99): 1;

preferably, in the step S1, the solid content of the amine-excessive polyamic acid solution is 13-18 wt%;

preferably, in the step S1, the reaction temperature is 0-50 ℃ and the reaction time is 0.5-3 h.

9. The method for preparing the matte insulated polyimide black film according to any one of claims 1 to 8, wherein in the step S2, the viscosity of the polyamic acid mixed solution is 1000 to 3000 poise.

10. A matte insulating polyimide black film, which is prepared by the preparation method of any one of claims 1 to 9.

Background

Polyimide films are widely used as a base material or a cover film material for flexible wiring boards because of their excellent heat resistance and excellent insulating and mechanical properties. However, the conventional polyimide film has high transparency and high glossiness, and has a problem of glare or astigmatism caused by light reflection in the application process, and a problem that the circuit design distribution may be interpreted and plagiarized by competitors. To solve the above problems, matte polyimide black films have come to be produced, which are characterized by low light transmittance and low gloss. The low light transmittance can shield an electronic circuit covered by the low light transmittance, so that reverse engineering is prevented; the low glossiness can solve the problems of glare and astigmatism, and the film has better appearance texture.

In order to provide polyimide films with low light transmittance and low gloss characteristics, a large amount of carbon black and a matting agent are generally incorporated into the films, but this process causes new problems. Carbon black has high conductivity, and when added into a thin film system, the carbon black can aggregate with each other to form a conductive path, so that the insulation property of the thin film is reduced, and the use of the carbon black in the electronic field is influenced. The matting agent is generally an inorganic substance with a specific particle size, such as silica, etc., and has poor compatibility with the polyimide system, and a large amount of matting agent needs to be added to achieve a desired glossiness, which may cause deterioration in film-forming properties, appearance, mechanical properties, etc. of the polyimide film.

The key point for solving the problems lies in improving the affinity of the additive and the polyimide system and improving the dispersion effect of the additive in the polyimide system. Chinese patent CN105482115B discloses that non-conductive carbon black is refluxed by concentrated sulfuric acid for 2 hours to modify and graft the surface of the non-conductive carbon black with — COOH, and silane coupling agent is used to improve the affinity between carbon black and polyimide, thereby improving the dispersion effect of carbon black in polyimide, but when the addition ratio of carbon black is large (for example, to prepare an ultrathin polyimide black film), the method has a limited effect. Chinese patent CN103160123B uses polyimide powder with an average particle size of 0.5-15 μm as a matting agent, has high insulation property compared with known inorganic matting agents, and has high affinity with polyimide systems, but the problem of poor compatibility between carbon black as a light-shading agent and polyimide systems has not been solved yet.

Disclosure of Invention

Based on the technical problems in the background art, the invention provides a matte insulating polyimide black film and a preparation method thereof.

The invention provides a preparation method of a matte insulating polyimide black film, which comprises the following steps:

s1, reacting aromatic dianhydride with aromatic diamine with molar quantity being excessive relative to the aromatic dianhydride in an aprotic polar solvent under inert atmosphere to obtain polyamide acid solution with excessive amine;

s2, adding silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, uniformly dispersing, and adding aromatic dianhydride for reaction to obtain polyamide acid mixed solution;

s3, forming and imidizing the polyamic acid mixed solution to obtain a matte insulating polyimide black film;

the total molar amount of the aromatic dianhydride added in steps S1 and S2 is equal to the molar amount of the aromatic diamine added in step S1.

Preferably, the average particle diameter of the silane coupling agent modified polyimide powder is 3 to 5 μm.

Preferably, the mass of the silane coupling agent modified polyimide powder is 3 to 5% of the sum of the mass of the aromatic dianhydride added in step S1 and the mass of the aromatic diamine added in step S1.

Preferably, the preparation method of the silane coupling agent modified polyimide powder comprises the following steps:

(a) in an inert atmosphere, stirring and reacting aromatic diamine and aromatic dianhydride with molar weight being excessive relative to the aromatic diamine in an aprotic polar solvent at 20-30 ℃ for 1-3 h to obtain polyamide acid solution with solid content being 1-5% wt and excessive anhydride;

(b) and adding an aminosilane coupling agent into the polyamide acid solution with excessive anhydride, stirring and reacting for 8-12 h at the temperature of 60-80 ℃, then adding a dehydrating agent and a catalyst, stirring and reacting for 8-12 h at the temperature of 80-100 ℃ to perform chemical imidization, after the reaction is finished, keeping the temperature of a reaction system at the temperature of 130-150 ℃ for 6-10 h, cooling, filtering, and washing, drying and crushing the obtained solid substance to obtain the polyamide acid.

Preferably, in the step (a), the inert atmosphere is a nitrogen atmosphere.

Preferably, in the step (a), the aprotic polar solvent is at least one of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP).

Preferably, in the step (a), the aromatic diamine is one or a combination of ODA and PDA, and the aromatic dianhydride is one or a combination of PMDA and BPDA.

Preferably, in the preparation method of the silane coupling agent modified polyimide powder, the molar ratio of the aromatic diamine to the aromatic dianhydride to the aminosilane coupling agent to the dehydrating agent to the catalyst is 1 (1.05-1.2) to (0.2-0.3) to (2-3) to (1.5-2.5).

Preferably, the aminosilane coupling agent is at least one of N-beta- (aminoethyl) -gamma-aminopropyl-trimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl-triethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl-methyldimethoxysilane, N-beta- (aminoethyl) -gamma-aminopropyl-methyldiethoxysilane, and N-gamma-aminoethylaminoethylaminopropyltrimethoxysilane.

Preferably, the dehydrating agent is acetic anhydride.

Preferably, the catalyst is isoquinoline.

Preferably, the solid content of the carbon black color paste is 8-12 wt%, and D₅₀＜300nm。。

Preferably, the mass of the carbon black color paste is 6-9% of that of the amine-excessive polyamic acid solution.

Preferably, the components of the carbon black color paste comprise carbon black and an aprotic polar solvent, and the preparation method of the carbon black color paste comprises the following steps: adding carbon black into an aprotic polar solvent, shearing at a high speed of 3000-5000 rpm for 30-60 min, and grinding for 30-60 min to obtain the carbon black, wherein the carbon black is the blue phase trough method carbon black with a primary particle size of 20-60 nm, and the aprotic polar solvent is at least one of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc) and N-methylpyrrolidone (NMP).

Preferably, in the step S1, the molar ratio of the aromatic dianhydride to the aromatic diamine is (0.97-0.99): 1.

Preferably, in step S1, the aromatic diamine is one or a combination of 4,4 '-diaminodiphenyl ether (ODA), p-Phenylenediamine (PDA), and 4,4' -diaminodiphenylmethane (DDM).

Preferably, in the step S1, the aromatic dianhydride is at least one of pyromellitic dianhydride (PMDA), 3',4,4' -biphenyltetracarboxylic dianhydride (BPDA), 3',4,4' -diphenylethertetracarboxylic dianhydride (ODPA), and bisphenol a type diether dianhydride (BPADA).

Preferably, in step S1, the aprotic polar solvent is at least one of N, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP).

Preferably, the aprotic polar solvent in the carbon black color paste is the same as the aprotic polar solvent in the step S1.

Preferably, in the step S1, the amine-excess polyamic acid solution has a solid content of 13-18 wt%.

Preferably, in the step S1, the reaction temperature is 0-50 ℃ and the reaction time is 0.5-3 h.

Preferably, in step S1, the inert atmosphere is a nitrogen atmosphere.

Preferably, in the step S2, the reaction temperature is 0 to 50 ℃.

Preferably, in the step S2, the dispersing method is high-speed shear dispersing, the dispersing rate is 1000 to 2000rpm, and the dispersing time is 30 to 60 min.

Preferably, in step S2, the polyamic acid mixture solution has a viscosity of 1000 to 3000 poise.

Preferably, in the step S3, the film forming includes casting or coating on a support, and drying, preferably, the drying temperature is 80 to 200 ℃, and the drying time is 15 to 120 min.

Preferably, in the step S3, the imidization method is thermal imidization, and the temperature of the thermal imidization is preferably 250 to 450 ℃ for 15 to 60 min.

In step S3, the polyamic acid mixture is preferably subjected to vacuum defoaming treatment before film formation to improve the film formation quality.

A matte insulating polyimide black film is prepared by the preparation method.

The invention has the following beneficial effects:

the method comprises the steps of reacting aromatic dianhydride with aromatic diamine with molar weight being excessive relative to the aromatic dianhydride in an aprotic polar solvent to obtain polyamide acid solution with excessive amine, adding silane coupling agent modified polyimide powder with the average particle size of 3-5 mu m and carbon black color paste into the solution, dispersing uniformly, adding the aromatic dianhydride for continuous reaction, wherein the silane coupling agent modified polyimide powder has good affinity and high insulation property with a polyimide film and can play a good light extinction effect in the polyimide film, and the solvent and the atmosphere inevitably contain trace water in the preparation process of the film, and molecular chain terminals in the silane coupling agent modified polyimide powder particles can form a large amount of silicon hydroxyl groups after absorbing water, and can react with hydrogen groups and carboxyl groups on the surface of the carbon black by a groove method to generate stable chemical bonds to further form a large-scale crosslinking net structure, therefore, with the addition of the subsequent aromatic dianhydride, the polyamic acid molecular chain continues to grow, and finally the polyamic acid molecular long chain is fully intertwined with the crosslinking network formed by the modified polyimide particles and the carbon black, so that the modified polyimide particles and the carbon black can be fully and uniformly distributed in the polyamic acid solution and the subsequent polyimide film.

The polyimide black film prepared by the invention has the characteristics of good appearance, low glossiness, high insulating strength and the like, the performances of tensile strength, elongation at break, thermal shrinkage and the like are improved, and the polyimide black film has excellent shading, matte, insulating and mechanical properties.

Detailed Description

The technical solution of the present invention will be described in detail below with reference to specific examples.

Example 1

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.5mol of ODA in a DMF solvent under the nitrogen atmosphere, then adding 0.525mol of PMDA, and stirring and reacting for 3 hours at the temperature of 20 ℃ to obtain a polyamic acid solution with 1 percent of solid content and excessive anhydride;

(b) adding 0.1mol of N-beta- (aminoethyl) -gamma-aminopropyl-trimethoxy silane into the polyamic acid solution with excessive anhydride, stirring and reacting for 12h at 60 ℃, then adding 1mol of acetic anhydride and 0.75mol of isoquinoline, stirring and reacting for 12h at 80 ℃, after the reaction is finished, preserving the temperature of the reaction system for 10h at 130 ℃, cooling, filtering, washing the obtained solid substance for 3 times by using ethanol solution, drying for 12h at 100 ℃ in a vacuum drying box, and crushing to obtain the product with the average particle size of 3 mu m.

Preparing carbon black color paste:

adding carbon black with primary particle size of 20nm into DMF solvent, high-speed shearing and dispersing at 3000rpm for 60min with high-speed shearing disperser, and grinding with pin-type sand mill for 60min to obtain solid content of 8 wt% and particle size distribution D₅₀Is 186nm carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 1mol of ODA in a DMF solvent under the nitrogen atmosphere, then adding 0.97mol of PMDA, and stirring and reacting for 3 hours at 0 ℃ to obtain a polyamide acid solution with solid content of 13% wt and excessive amine;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 60min at 1000rpm, adding 0.03mol of PMDA, and carrying out stirring reaction at 0 ℃ to obtain a polyamide acid mixed solution with the viscosity of 1800 poise, wherein the mass of the silane coupling agent modified polyimide powder is 3% of the sum of the mass of ODA in S1 and the mass of PMDA in S1, and the mass of the carbon black color paste is 6% of the mass of the polyamide acid solution with excessive amine in S1;

s3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 40min at 80 ℃, 40min at 100 ℃ and 40min at 120 ℃ in sequence, then performing heat preservation treatment for 10min at 250 ℃, 280 ℃, 300 ℃, 320 ℃, 340 ℃ and 360 ℃ in sequence for thermal imidization, naturally cooling and peeling to obtain the matte insulating polyimide black film with the thickness of 12.5 mu m.

Example 2

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.5mol of PDA in a DMAc solvent under the nitrogen atmosphere, then adding 0.55mol of PMDA, and stirring and reacting for 2 hours at 25 ℃ to obtain a polyamide acid solution with 1 wt% of solid content and excessive anhydride;

(b) adding 0.125mol of N-beta- (aminoethyl) -gamma-aminopropyl-triethoxysilane into the polyamic acid solution with excessive anhydride, stirring and reacting for 12h at 60 ℃, then adding 1.25mol of acetic anhydride and 1mol of isoquinoline, stirring and reacting for 12h at 80 ℃, after the reaction is finished, preserving the temperature of the reaction system for 10h at 130 ℃, cooling, filtering, washing the obtained solid substance for 3 times by using an ethanol solution, drying for 12h at 100 ℃ in a vacuum drying oven, and crushing to obtain the product with the average particle size of 3 mu m.

Preparing carbon black color paste:

adding carbon black with primary particle size of 30nm into DMF solvent, high-speed shearing and dispersing at 3000rpm for 60min with high-speed shearing disperser, and grinding with pin-type sand mill for 60min to obtain solid content of 8 wt% and particle size distribution D₅₀Is 198nm carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 0.7mol of ODA and 0.3mol of PDA in a DMF solvent under a nitrogen atmosphere, then adding 0.97mol of PMDA, and stirring and reacting at 10 ℃ for 2.5h to obtain a polyamide acid solution with 14% wt of solid content and excessive amine;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 1h at 1000rpm, adding 0.03mol of PMDA, and carrying out stirring reaction at 10 ℃ to obtain polyamide acid mixed solution with the viscosity of 1300 poise, wherein the mass of the silane coupling agent modified polyimide powder is 3% of the sum of the masses of ODA, PDA and PMDA in S6356, and the mass of the carbon black color paste is 6% of the mass of the polyamide acid solution with excessive amine in S1;

s3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 40min at 80 ℃, 40min at 100 ℃ and 40min at 120 ℃ in sequence, then performing heat preservation treatment for 10min at 250 ℃, 280 ℃, 300 ℃, 320 ℃, 340 ℃ and 360 ℃ in sequence for thermal imidization, naturally cooling and peeling to obtain the matte insulating polyimide black film with the thickness of 12.5 mu m.

Example 3

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.4mol of ODA and 0.1mol of PDA in an NMP solvent in a nitrogen atmosphere, then adding 0.55mol of BPDA, and stirring and reacting for 2 hours at 25 ℃ to obtain a polyamic acid solution with excessive anhydride and 3 wt% of solid content;

(b) adding 0.125mol of N-beta- (aminoethyl) -gamma-aminopropyl-methyldimethoxysilane into the excessive polyamic acid solution, stirring and reacting for 10h at 70 ℃, then adding 1.25mol of acetic anhydride and 1mol of isoquinoline, stirring and reacting for 10h at 90 ℃, after the reaction is finished, preserving the temperature of the reaction system for 8h at 140 ℃, cooling, filtering, washing the obtained solid substance for 3 times by using ethanol solution, drying for 12h at 100 ℃ in a vacuum drying oven, and crushing to obtain the product with the average particle size of 4 mu m.

Preparing carbon black color paste:

adding carbon black with primary particle size of 30nm into DMAc solvent, high-speed shearing and dispersing at 4000rpm for 45min by using a high-speed shearing and dispersing machine, and grinding for 45min by using a pin-type sand mill to obtain the carbon black with solid content of 10 wt% and particle size distribution D₅₀Is 203nm of carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 1mol of DDM in DMAc solvent under the nitrogen atmosphere, then adding 0.5mol of PMDA and 0.48mol of BPDA, and stirring and reacting for 2 hours at 20 ℃ to obtain amine excess polyamic acid solution with solid content of 15% wt;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 45min at 1500rpm, adding 0.02mol of PMDA, and stirring for reaction at 20 ℃ to obtain polyamide acid mixed solution with the viscosity of 1000 poise, wherein the mass of the silane coupling agent modified polyimide powder is 4% of the sum of the mass of DDM in S1 and the mass of PMDA and BPDA in S1, and the mass of the carbon black color paste is 7.5% of the mass of the polyamide acid solution with excessive amine in S1;

and S3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 20min at 100 ℃, 20min at 140 ℃, 20min at 180 ℃, then respectively performing heat preservation treatment for 10min at 280 ℃, 350 ℃ and 420 ℃ in sequence to perform thermal imidization, naturally cooling and peeling to obtain the matte insulating polyimide black film with the thickness of 12.5 mu m.

Example 4

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.5mol of ODA in a DMF solvent under the nitrogen atmosphere, then adding 0.5mol of PMDA and 0.05mol of BPDA, and stirring and reacting for 2 hours at 25 ℃ to obtain a polyamic acid solution with excessive anhydride and 3 wt% of solid content;

(b) adding 0.125mol of N-beta- (aminoethyl) -gamma-aminopropyl-methyldiethoxysilane into the excessive polyamic acid solution, stirring and reacting at 70 ℃ for 10h, then adding 1.25mol of acetic anhydride and 1mol of isoquinoline, stirring and reacting at 90 ℃ for 10h, after the reaction is finished, preserving the temperature of the reaction system at 140 ℃ for 8h, cooling, filtering, washing the obtained solid substance with ethanol solution for 3 times, drying in a vacuum drying oven at 100 ℃ for 12h, and crushing to obtain the product with the average particle size of 4 mu m.

Preparing carbon black color paste:

adding carbon black with primary particle size of 40nm into DMAc solvent, high-speed shearing and dispersing at 4000rpm for 45min by using a high-speed shearing and dispersing machine, and grinding for 45min by using a pin-type sand mill to obtain the carbon black with solid content of 10 wt% and particle size distribution D₅₀Is 215nm carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 0.8mol of ODA and 0.2mol of PDA in a DMAc solvent in a nitrogen atmosphere, then adding 0.98mol of PMDA, and stirring and reacting at 30 ℃ for 1.5h to obtain a polyamic acid solution with 16% wt of solid content and excessive amine;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 1h at 1000rpm, adding 0.02mol of PMDA, and carrying out stirring reaction at 30 ℃ to obtain a polyamide acid mixed solution with the viscosity of 3000 poise, wherein the mass of the silane coupling agent modified polyimide powder is 4% of the sum of the masses of ODA, PDA and PMDA in S1 in S1, and the mass of the carbon black color paste is 7.5% of the mass of the polyamide acid solution with excessive amine in S1;

and S3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 20min at 100 ℃, 20min at 140 ℃, 20min at 180 ℃, then respectively performing heat preservation treatment for 10min at 280 ℃, 350 ℃ and 420 ℃ in sequence to perform thermal imidization, naturally cooling and peeling to obtain the matte insulating polyimide black film with the thickness of 12.5 mu m.

Example 5

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.5mol of PDA in a DMAc solvent under the nitrogen atmosphere, then adding 0.55mol of BPDA, and stirring and reacting for 1h at the temperature of 30 ℃ to obtain a polyamic acid solution with 5 wt% of solid content and excessive anhydride;

(b) adding 0.125mol of N-gamma-aminoethyl aminopropyl trimethoxy silane into the polyamic acid solution with excessive anhydride, stirring and reacting for 8h at 80 ℃, then adding 1.25mol of acetic anhydride and 1mol of isoquinoline, stirring and reacting for 8h at 100 ℃, after the reaction is finished, preserving the temperature of the reaction system for 6h at 150 ℃, cooling, filtering, washing the obtained solid substance with ethanol solution for 3 times, drying for 12h at 100 ℃ in a vacuum drying box, and crushing to obtain the product with the average particle size of 5 mu m.

Preparing carbon black color paste:

adding blue phase groove method carbon black with primary particle size of 50nm into NMP solvent, and high-speed shearing at 5000rpm with high-speed shearing disperserCutting and dispersing for 30min, and grinding for 30min by using a pin type sand mill to obtain the product with the solid content of 12 wt% and the particle size distribution D₅₀Is 258nm carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 0.5mol of ODA and 0.5mol of PDA in an NMP solvent in a nitrogen atmosphere, then adding 0.99mol of BPDA, and stirring and reacting for 1h at 40 ℃ to obtain a polyamide acid solution with 17% wt of solid content and excessive amine;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 1h at 1000rpm, adding 0.01mol of BPDA, and carrying out stirring reaction at 40 ℃ to obtain a polyamide acid mixed solution with the viscosity of 2500 poise, wherein the mass of the silane coupling agent modified polyimide powder is 5% of the sum of the mass of ODA in S1, the mass of PDA and the mass of BPDA in S1, and the mass of the carbon black color paste is 9% of the mass of the polyamide acid solution with excessive amine in S1;

s3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 5min at 120 ℃, 5min at 160 ℃, 5min at 200 ℃, then respectively preserving heat for 5min at 300 ℃, 380 ℃ and 450 ℃ in sequence for thermal imidization, naturally cooling and stripping to obtain the matte insulating polyimide black film with the thickness of 12.5 microns.

Example 6

Preparing silane coupling agent modified polyimide powder:

(a) dissolving 0.5mol of ODA in an NMP solvent in a nitrogen atmosphere, then adding 0.6mol of BPDA, and stirring and reacting for 1h at the temperature of 30 ℃ to obtain a polyamic acid solution with 5 wt% of solid content and excessive anhydride;

(b) adding 0.1mol of N-gamma-aminoethyl aminopropyl trimethoxy silane and 0.05mol of N-beta- (aminoethyl) -gamma-aminopropyl-triethoxy silane into the polyamic acid solution with excessive anhydride, stirring and reacting for 8h at 80 ℃, then adding 1.5mol of acetic anhydride and 1.25mol of isoquinoline, stirring and reacting for 8h at 100 ℃, after the reaction is finished, preserving the temperature of the reaction system for 6h at 150 ℃, cooling, filtering, washing the obtained solid substance with ethanol solution for 3 times, drying for 12h at 100 ℃ in a vacuum drying oven, and crushing to obtain the product with the average particle size of 5 mu m.

Preparing carbon black color paste:

adding blue phase groove method carbon black with primary particle size of 60nm into NMP solvent, high-speed shearing and dispersing for 30min at 5000rpm by using a high-speed shearing dispersion machine, and grinding for 30min by using a pin type sand mill to obtain the product with solid content of 12 wt% and particle size distribution D₅₀Is 283nm carbon black color paste.

Preparing a matte insulating polyimide black film:

s1, dissolving 1mol of ODA in NMP solvent in nitrogen atmosphere, then adding 0.99mol of BPDA, stirring and reacting for 0.5h at 50 ℃ to obtain polyamide acid solution with excessive amine and 18% wt of solid content;

s2, adding the prepared silane coupling agent modified polyimide powder and carbon black color paste into the polyamide acid solution with excessive amine, carrying out high-speed shearing dispersion for 60min at 1000rpm, adding 0.01mol BPDA, and carrying out stirring reaction at 50 ℃ to obtain a polyamide acid mixed solution with the viscosity of 1300 poise, wherein the mass of the silane coupling agent modified polyimide powder is 5% of the sum of the mass of ODA in S1 and the mass of BPDA in S1, and the mass of the carbon black color paste is 9% of the mass of the polyamide acid solution with excessive amine in S1;

s3, casting the polyamic acid mixed solution on a glass plate after vacuum defoaming treatment, drying for 5min at 120 ℃, 5min at 160 ℃, 5min at 200 ℃, then respectively preserving heat for 5min at 300 ℃, 380 ℃ and 450 ℃ in sequence for thermal imidization, naturally cooling and stripping to obtain the matte insulating polyimide black film with the thickness of 12.5 microns.

Comparative example 1

Comparative example 1 differs from example 1 only in that: fumed silica having an average particle diameter of 3 μm was used as a matting agent in place of the silane coupling agent-modified polyimide powder.

Comparative example 2

Comparative example 2 differs from example 1 only in that: polyimide powder with the average particle size of 3 mu m is adopted to replace silane coupling agent modified polyimide powder as a delustering agent, wherein the preparation method of the polyimide powder comprises the following steps:

(a) dissolving 0.5mol of ODA in a DMF solvent under the nitrogen atmosphere, then adding 0.525mol of PMDA, and stirring and reacting for 3 hours at the temperature of 20 ℃ to obtain a polyamic acid solution with 1 percent of solid content and excessive anhydride;

(b) adding 1mol of acetic anhydride and 0.75mol of isoquinoline into the polyamic acid solution, stirring and reacting at 80 ℃ for 12h, after the reaction is finished, keeping the temperature of the reaction system at 130 ℃ for 10h, cooling, filtering, washing the obtained solid substance for 3 times by using an ethanol solution, drying in a vacuum drying oven at 100 ℃ for 12h, and crushing to obtain the polyamic acid solution with the average particle size of 3 microns.

Comparative example 3

Comparative example 3 differs from example 1 only in that: a silane coupling agent-modified polyimide powder having an average particle size of 2 μm was used as a matting agent in place of the silane coupling agent-modified polyimide powder having an average particle size of 3 μm in example 1, wherein the silane coupling agent-modified polyimide powder having an average particle size of 2 μm and the silane coupling agent-modified polyimide powder having an average particle size of 3 μm in example 1 were prepared by the same method except that the average particle size after pulverization was different.

Comparative example 4

Comparative example 4 differs from example 1 only in that: a silane coupling agent-modified polyimide powder having an average particle size of 6 μm was used as a matting agent in place of the silane coupling agent-modified polyimide powder having an average particle size of 3 μm in example 1, wherein the silane coupling agent-modified polyimide powder having an average particle size of 6 μm and the silane coupling agent-modified polyimide powder having an average particle size of 3 μm in example 1 were prepared by the same method except that the average particle size after pulverization was different.

The films prepared in the above examples 1 to 6 and comparative examples 1 to 4 were subjected to a performance test with reference to ASTM D1003 and ASTM D523 as a test standard for light transmittance and gloss, ASTM D149 as a test standard for dielectric strength, ASTM D882 as a test standard for tensile strength and breaking productivity, IPC TM6502.2.4A as a test standard for heat shrinkage; the test results are shown in table 1:

TABLE 1 film Performance test results

As can be seen from examples 1 to 6 in Table 1, the polyimide black film sample with high shading, high matte, high insulation, and excellent mechanical properties and thermal stability can be prepared by the preparation method provided by the invention. In comparative example 1, when fumed silica having an average particle size of 3 μm was used as a matting agent instead of the modified polyimide powder, a matting effect similar to that of example 1 was obtained, but the light-shielding property, the insulating strength, the tensile strength and other properties of the film sample were significantly deteriorated. In comparative example 2, the polyimide powder with the average particle size of 3 μm and without modification by amino silane coupling agent is used as the delustering agent, the delustering effect similar to that of example 1 can be achieved, and other performances of the film sample are improved to a certain extent compared with those of comparative example 1, but a certain gap is left between the film sample and the example 1. In comparative example 3, the polyimide powder modified with the aminosilane coupling agent having an average particle size of 2 μm was used as a matting agent, and although all of the other indices were excellent, the degree of gloss was high and did not meet the desired matte effect. In comparative example 4, in which the polyimide powder modified with the aminosilane coupling agent having an average particle diameter of 6 μm was used as a matting agent, the film sample had low gloss but the insulation properties and mechanical properties were significantly deteriorated.

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