CN109135280B

CN109135280B - Low-pinhole-occurrence-rate high-insulation matte black polyimide film and preparation method thereof

Info

Publication number: CN109135280B
Application number: CN201810971261.6A
Authority: CN
Inventors: 青双桂; 白小庆; 姬亚宁; 冯羽风; 白蕊; 全光好
Original assignee: Guilin Electrical Equipment Scientific Research Institute Co Ltd
Current assignee: Guilin Electrical Equipment Scientific Research Institute Co Ltd
Priority date: 2018-08-24
Filing date: 2018-08-24
Publication date: 2021-03-05
Anticipated expiration: 2038-08-24
Also published as: CN109135280A

Abstract

The invention discloses a low-pinhole-occurrence high-insulation matte black polyimide film and a preparation method thereof. The preparation method comprises the following steps: 1) mixing black dispersion liquid with a solute of carbon black and white dispersion liquid with a solute of a flatting agent, performing shear dispersion and/or ultrasonic dispersion on the obtained mixed liquid, adding a non-metal alkoxide and a polyamic acid resin solution, and performing shear dispersion and/or ultrasonic dispersion to obtain black filler dispersion liquid; 2) in a polar aprotic solvent, the ratio of 1: adding diamine and dianhydride in a molar ratio of 0.990-0.998 to react to prepare polyamic acid resin solution, adding black filler dispersion liquid, stirring uniformly, adding or not adding a stabilizer, and stirring uniformly to obtain matte black PAA resin solution; 3) the obtained matte black PAA resin solution is further prepared into a matte black PI film. The film prepared by the method has excellent insulating property, better mechanical property and lower pinhole and bubble rate.

Description

Low-pinhole-occurrence-rate high-insulation matte black polyimide film and preparation method thereof

Technical Field

The invention relates to a polyimide film, in particular to a low-pinhole-occurrence high-insulation matte black polyimide film and a preparation method thereof.

Background

In recent years, matte black Polyimide (PI) films have been used to cover electronic materials such as flexible wiring boards, electronic components, lead frames of integrated circuit packages, and the like, in order to prevent visual inspection and tampering. The matte black PI film is usually made by adding carbon black with strong coloring power into the PI film to make the film opaque black. The carbon black is composed of carbon, the arrangement mode of carbon atoms is similar to that of graphite, the carbon black has conductivity, the nano carbon black network chains are tightly stacked, the specific surface area is large, the number of particles per unit mass is large, and a chain type conductive structure is easily formed in a polymer. Therefore, the addition of the nano-scale carbon black not only blackens the film, but also reduces the insulation of the PI film, resulting in a significant drop in electrical strength. If the carbon black is agglomerated, the network chain is more tightly stacked, and the large-area distribution is uneven, so that the electrical strength is further reduced, the electrical strength of each film is different, the films are short-circuited in later application, and the product quality of the electronic product is directly influenced.

The electrical strength is taken as a key performance in various technical indexes of the polyimide film for the electronic product, and plays an important role in the stability of the electronic product. Taking a matte black PI film with the thickness of 12.5 mu m as an example, the electric strength performance and the appearance difference of the existing film with the thickness on the market are larger, the electric strength of the imported matte black PI film is between 90 and 130kV/mm, and the number of air bubbles and pinholes on the appearance of the film surface is less; the electric strength of domestic matt black PI films is mostly 60-80kV/mm, and the air bubbles and pinholes on the film surfaces are uneven. In the aspect of appearance quality, the film surface of the domestic matt black PI film has a large number of pinholes and bubbles, so that the insulativity of the matt black PI film is reduced, and the quality of the manufactured electronic product is adversely affected.

For domestic manufacturers, the matte black PI film prepared by the prior art is mostly about 80kV/mm, and the main methods comprise the following steps: the method adopts coupling agent modified carbon black, organic dye substituted or partially substituted carbon black, inorganic oxide substituted carbon black, other opacifier substituted partial carbon black or prepares more than two layers of black PI films and the like, but has a plurality of defects in the actual production process. For example, a method of modifying carbon black with a coupling agent, such as poor control of the coupling agent, may result in self-condensation, whereby formation of foreign particles causes generation of pinholes and bubbles; the tinting strength of the organic black dye is not as good as that of the carbon black, at least several times of the tinting strength of the organic black dye is needed to obtain the black PI film with the same shading effect as the carbon black, and the organic black dye has poor heat resistance and directly influences the heat resistance of the matte black PI film after being added; the black metal oxide has high density, is easy to settle, affects the consistency of film products, and the electronic products exported to European Union must pass the European Union environmental protection standard, and can not detect tin, cobalt and other metal elements in the products, which also causes the technology to be limited in the actual product production; by adopting the matt black PI film with a double-layer or multi-layer design structure, if the thickness is not uniform, the problems of warping, uneven tension and the like are easy to occur, great trouble is caused to downstream customers for gluing, and the difficulty of the preparation process is great.

The invention patent with publication number CN102482418A adopts various filler dispersing equipment and a dispersing process to combine to prepare a low-matt black PI film with the thickness of 15 mu m. In a specific example, 10 wt% of low conductivity carbon black, 10 wt% of PAA resin and 80 wt% of solvent are mixed uniformly in a high-speed dispersion mill by a partial chemical imidization method, and then ball-milled by a ball mill to obtain carbon black slurry with a median particle size of 300 nm. Subsequently, 15% by weight of silica matting powder, 9.6% by weight of a resin and 75.4% by weight of a solvent were uniformly mixed in a high-speed stirrer to obtain silica matting powder slurry having a median particle size of 3.6 μm. Next, the black slurry and PAA resin were mixed uniformly in a mixing vessel equipped with a low speed anchor stirrer, a high speed disk disperser, and a high speed shear rotor-stator emulsifier. Adding matting powder slurry, thoroughly mixing with a high-speed shearing rotor-stator stirrer to obtain matte black PAA resin with resin viscosity of more than 1200 poise, and preparing into film by chemical imidization method to obtain the final product with double-side glossiness of 12GU, electric intensity of 106kV/mm, and surface resistivity of 10¹⁵Omega, a matte black PI film with an optical density of 4.31. Although the black slurry and the matting powder slurry which are uniformly dispersed can be obtained by the method, the dispersing process of the black slurry and the matting powder slurry is complicated, particularly in the process of grinding the carbon black slurry and the PAA resin, the good sealing property of a container must be ensured, otherwise, the PAA resin is easy to absorb water, so that hydrolysis is caused, even the agglomeration of the filler is influenced, and pinholes and bubbles are generated.

For reducing matt blackThe invention discloses pinholes and bubbles on the appearance of a PI film surface, and discloses a specific scheme in an invention patent with the publication number of CN104169330A, wherein 3.0-7.5 wt% of carbon black and 0.5-1.5 wt% of TiO₂The shielding agent is added into the polyamic acid resin to prepare the film, the light transmittance of the obtained film is lower than 1.0 percent, the glossiness is lower than 60 percent, the elongation at break is greater than 80 percent, and the surface resistivity is greater than 10¹⁵Omega, pinhole incidence below 1/100m². However, the invention also clearly indicates that when the amount of the shielding agent added is 0.5 to 1.5 wt%, the resulting film has good processability, heat radiation and shielding properties, but when it is more than 1.5 wt%, the resulting film is deteriorated in mechanical properties, the incidence of pinholes is increased, resulting in a decrease in film yield and poor appearance. However, in order to seek a better matte effect, the mass fraction of the matting powder added to the polyamic acid resin is more than 3 wt% to achieve the purpose of reducing the glossiness of the black PI film. It can be seen that the method of the above invention does not address the consumer needs of the prior art.

Therefore, how to solve the problem that the inferior gloss black PI film has low insulation and the occurrence rate of pinholes and bubbles can be reduced becomes the problem of improving the quality of the inferior gloss black PI film product in China.

Disclosure of Invention

The invention aims to solve the technical problem of providing a low-pinhole-occurrence-rate high-insulation matte black polyimide film and a preparation method thereof. The matt black polyimide film prepared by the method has excellent insulating property, better mechanical property and lower pinhole and bubble rate.

In order to solve the technical problems, the preparation method of the matte black polyimide film with low pinhole incidence and high insulation provided by the invention comprises the following steps:

1) preparation of the black filler dispersion:

1.1) uniformly dispersing carbon black in a polar aprotic solvent to obtain a black dispersion liquid;

1.2) uniformly dispersing the delustering agent in a polar aprotic solvent to obtain a white dispersion liquid;

1.3) mixing the black dispersion liquid and the white dispersion liquid, carrying out shear dispersion and/or ultrasonic dispersion on the obtained mixed liquid, then adding non-metal alkoxide, carrying out shear dispersion and/or ultrasonic dispersion, then adding a polyamic acid resin solution, and carrying out shear dispersion and/or ultrasonic dispersion to obtain a black filler dispersion liquid; wherein, the non-metal alkoxide is one or the combination of more than two of tetrabutyl titanate (TBT), ethyl titanate, tetraethyl orthosilicate (TEOS) and methyl orthosilicate (TMOS), and the addition amount of the non-metal alkoxide is 0.1 to 5 weight percent of the total amount of the carbon black and the flatting agent; the solid content of the polyamic acid resin solution is 17-22 wt%, and the adding amount of the polyamic acid resin solution is 1-9 wt% of the total using amount of the carbon black and the flatting agent;

2) in a polar aprotic solvent, the ratio of 1: adding aromatic diamine and aromatic dianhydride in a molar ratio of 0.990-0.998 to react to prepare polyamic acid resin solution, then adding black filler dispersion liquid, stirring uniformly, then adding or not adding a stabilizer, and stirring uniformly to obtain matt black polyamic acid resin solution; the stabilizer is triphenyl phosphate and/or triphenyl phosphite;

3) the black matt polyimide film is prepared from the obtained matt black polyamic acid resin solution according to the conventional process.

In steps 1.1) and 1.2) of the above preparation method, the carbon black or the matting agent can be uniformly dispersed in the polar aprotic solvent by the conventional method, and the carbon black or the matting agent is preferably dispersed by the following method, so that the carbon black or the matting agent has better mechanical properties, electrical properties and glossiness while the lower pinhole rate is obtained:

putting carbon black into polar aprotic solvent, shearing and dispersing, and then carrying out homogenization treatment or grinding treatment or ultrasonic dispersion to obtain black dispersion liquid. Wherein, the shearing dispersion is preferably carried out under the condition of the rotating speed of 1000-3000r/min, and the time of the shearing dispersion is more than or equal to 0.5h, preferably 0.5-3 h; the homogenization treatment is carried out under the condition that the pressure is less than or equal to 50MPa, and the homogenization time is more than or equal to 15min, preferably 30-90 min; the grinding treatment is carried out at the rotating speed of 1000-3000r/min, and the grinding time is more than or equal to 0.5h, preferably 0.5-3 h; the time of ultrasonic dispersion is more than or equal to 0.5h, preferably 0.5-3 h.

The delustering agent is placed in a polar aprotic solvent for shearing dispersion to obtain a white dispersion liquid, the shearing dispersion is carried out at the rotating speed of 1000-3000r/min, and the shearing dispersion time is not less than 0.5h, preferably 1-5 h.

In step 1.3) of the preparation method, in order to obtain the black filler dispersion liquid with better dispersibility, the shear dispersion is preferably carried out at a rotation speed of 1000-; the time for ultrasonic dispersion is preferably not less than 1 hour, more preferably 2 to 3 hours. The polyamic acid resin solution in the step is prepared according to the conventional method, for example, the polyamic acid resin solution is prepared by carrying out polycondensation reaction on known aromatic diamine and aromatic dianhydride in a polar aprotic solvent; the polyamic acid resin solution is preferably added in an amount of 3 to 6 wt% based on the total amount of carbon black and matting agent. The amount of the non-metal alkoxide added in this step is preferably 1 to 2% by weight of the total amount of the carbon black and the matting agent.

In step 1) of the preparation method, the matting agent is a conventional choice in the prior art, and is preferably one or a combination of any two or more selected from silicon dioxide, titanium dioxide and calcium hydrogen phosphate. The matting agent is usually a matting agent having an average particle diameter of 1 to 10 μm, preferably 2 to 10 μm, and more preferably 3 to 8 μm. The carbon black is usually a carbon black having a surface resistance of 10 or more⁸The primary particle diameter of the low-conductive carbon black of Ω is usually 5 to 300nm, preferably 10 to 200nm, and more preferably 15 to 100 nm.

In step 2) of the preparation method, the addition amount of the black filler dispersion is controlled to be the amount in which the carbon black and the matting agent are added conventionally in the prior art, preferably, the addition amount of the carbon black is controlled to be 2 to 7 wt% of the solid content of the polyamic acid resin solution in step 2), and the addition amount of the matting agent is 1 to 8 wt% of the solid content of the polyamic acid resin solution in step 2); it is further preferable to control the amount of carbon black added therein to be 3 to 5 wt% of the solid content of the polyamic acid resin solution in step 2), and the amount of matting agent added therein to be 3 to 7 wt% of the solid content of the polyamic acid resin solution in step 2). The solid content of the polyamic acid resin solution described in this step may be the same as that of the prior art, and is preferably 17 to 22 wt%, preferably 18 to 21 wt%, and more preferably 19 to 20 wt%.

In step 2) of the above preparation method, the stabilizer is added to inhibit thermal decomposition, and the addition amount is the same as that in the prior art, specifically, the addition amount is 0.5-2 wt% of the solid content of the polyamic acid resin solution in step 2), and when the mixture of triphenyl phosphate and triphenyl phosphite is added, the ratio of the triphenyl phosphate and triphenyl phosphite can be any ratio on the premise that the total addition amount meets the above requirements.

In the step 3) of the preparation method, the black matt polyimide film is prepared from the obtained matt black polyamic acid resin solution through defoaming, casting, stretching and thermal imidization.

The selection and the dosage of the polar aprotic solvent, the aromatic diamine and the aromatic dianhydride related to the method of the invention are the same as those of the prior art, and the temperature and the time for the polycondensation reaction of the aromatic diamine and the aromatic dianhydride are also the same as those of the prior art. The following are preferred:

the aromatic diamine may be one or a combination of two or more selected from 4,4 '-diaminodiphenyl ether (ODA), 3, 4' -diaminodiphenyl ether, 3 '-diaminodiphenyl ether, 1, 4-diaminobenzene (p-PDA), 1, 3-diaminobenzene (m-PDA), 1, 2-diaminobenzene (o-PDA), 4' -Diaminobiphenyl (DBZ), 4 '-diamino-3, 3' -dimethylbiphenyl (OTD), 4 '-diamino-2, 2' -dimethylbiphenyl (MTD). When the aromatic diamine is selected from the above two or more kinds of diamines, the ratio of the aromatic diamine to the aromatic diamine can be arbitrarily determined.

The aromatic dianhydride may be one or a combination of any two or more selected from pyromellitic dianhydride (PMDA), 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3 ', 4' -biphenyltetracarboxylic dianhydride (a-BPDA), 3,3 ', 4, 4' -diphenylethertetracarboxylic dianhydride (ODPA), 2,3,3 ', 4' -diphenylethertetracarboxylic dianhydride, 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride (BTDA), and 2,3,3 ', 4' -benzophenonetetracarboxylic dianhydride. When the aromatic dianhydride is selected from the above two or more compounds, the ratio of the aromatic dianhydride to the aromatic dianhydride can be arbitrarily determined. The reaction temperature may be 0 to 80 ℃, preferably 0 to 60 ℃, more preferably 0 to 50 ℃ and the reaction time is usually 5 to 40 hours.

The polar aprotic solvent may be one or a combination of any two or more selected from N, N-Dimethylacetamide (DMAC), N-Dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N-diethylacetamide and N, N-diethylformamide; when the polar aprotic solvent is selected from the above-mentioned two or more kinds of combinations, the ratio therebetween may be any ratio.

The invention also discloses the matte black polyimide film with low pinhole incidence and high insulation, which is prepared by the method.

Compared with the prior art, the invention is characterized in that:

1. the non-metal alkoxide is added into the mixed liquid of the black dispersion liquid and the white dispersion liquid, and the non-metal alkoxide and the water in the pores of the filler or the water discharged from the pores are subjected to chemical hydrolysis reaction to generate a semi-inorganic or inorganic network structure, so that on one hand, the black dispersion liquid and the white dispersion liquid are stabilized and prevented from settling, on the other hand, the compatibility of the filler and resin is increased, and the generation of film pinholes and bubbles is greatly reduced. The nonmetal alkoxide which is not completely hydrolyzed can still consume the water generated by the condensation of the polyamic acid resin when being mixed with the polyamic acid resin subsequently, thereby avoiding the generation of pinholes and bubbles caused by the existence of the water. And adding a specific amount of polyamic acid resin to coat the carbon black and the extinction powder filler after the nonmetal alkoxide so as to form an insulating layer on the surface of the carbon black and prevent the formation of a carbon black conductive network chain structure, thereby effectively improving the insulativity of the film.

2. The molar ratio of diamine to dianhydride is defined as 1: 0.990 to 0.998, the local gels of the molecular segments are prevented from forming agglomerated cores which lead to agglomeration of the filler (these agglomerates are also one of the causes of pinholes and bubbles), thereby further reducing the generation of pinholes and bubbles.

3. Further, a black dispersion liquid and a white dispersion liquid are obtained by adopting a specific dispersion method, more than two kinds of particles are mixed to be mutually interpenetrated, then ultrasonic dispersion or shear dispersion is carried out, so that the filler is fully soaked by the solvent, and is replaced with air and water in pores, and finally the filler is mixed with the polyamic acid resin, so that the problem of poor wettability caused by difficult discharge of air or water due to the specific surface area of the carbon black and the matting agent is solved, and the generation of pinholes and bubbles in the film making process is reduced from the other aspect.

4. The matt black PI film prepared by the method has excellent insulating property, better mechanical property and glossiness and lower pinhole and bubble rate, and takes a matt black PI film with the thickness of 13 mu m as an example, the matt black PI film has the tensile strength of more than or equal to 180MPa, the elongation at break of more than or equal to 45 percent and the volume resistivity of more than or equal to 10¹²Omega.m, surface resistivity of not less than 10¹⁶Omega, the electrical strength is more than or equal to 120kV/mm, the pinhole and bubble occurrence rate of the film is less than 0.5 per 100m²。

Detailed Description

The present invention will be better understood from the following detailed description of specific examples, which should not be construed as limiting the scope of the present invention.

The polyamic acid resin solution for coating carbon black and matting agent (i.e. the polyamic acid resin solution added in step 1.3) referred to in the following examples was obtained by polycondensation reaction of the conventional diamine and dianhydride in a polar aprotic solvent, wherein the solid content of each numbered resin solution and the molar ratio of the diamine and dianhydride are shown in the following table 1:

table 1:

example 1

1) Preparation of the black filler dispersion:

1.1) uniformly mixing 4.2kg of carbon black (primary particle size is 20nm) and 38kg of DMAc, shearing and dispersing by using a high-speed shearing machine (the rotating speed is 2000r/min, the dispersing time is 1h), and dispersing by using a homogenizer (the pressure is 50MPa, and the homogenizing time is 30min) to obtain a black dispersion liquid for later use;

1.2) uniformly mixing 4.2kg of silicon dioxide (with the average particle size of 4 mu m) and 24kg of DMAc, and placing the mixture in a high-speed shearing machine to shear and disperse for 3 hours at the rotating speed of 3000r/min to obtain white dispersion liquid for later use;

1.3) mixing the black dispersion liquid and the white dispersion liquid, putting the obtained mixed liquid into a high-speed shearing machine, adding 85g of n-butyl titanate, shearing and dispersing for 10h at the rotating speed of 2000r/min, then putting the mixed liquid into ultrasonic equipment for ultrasonic dispersion for 2h, finally adding 420g of PAA-1 resin, shearing and stirring for 2h at the rotating speed of 2000r/min to obtain black filler dispersion liquid;

2) adding 0.2mol of ODA into 310kg of DMAc, and adding 0.1988mol of PMDA in multiple times after complete dissolution to react to obtain a polyamic acid resin solution; then adding black filler dispersion liquid, fully and uniformly stirring, then adding 200g of triphenyl phosphite, and continuously and uniformly stirring to obtain a matte black polyamic acid resin solution;

3) defoaming the obtained matte black polyamic acid resin solution, coating the resin on a steel belt through a scraper or an extrusion die head, heating (170 ℃) to remove the solvent to obtain a self-supporting film, and then performing unidirectional/bidirectional stretching and thermal imidization (420 ℃) to obtain a matte black PI film with the thickness of 13 mu m.

Example 2

Example 1 was repeated except that:

in the step 1.3), the non-metal alkoxide is tetraethoxysilane, and the addition amount of the PAA-1 resin is 84 g;

in the step 2), the total amount of PMDA is 0.1994 mol;

in steps 1) and 2), the polar aprotic solvent was changed to NMP.

Example 3

Example 1 was repeated except that:

in the step 1.1), the primary particle size of the carbon black is 300 nm;

in the step 1.3), the nonmetal alkoxide is tetraethoxysilane, and the adding amount of the PAA-1 resin is 670 g.

Example 4

Example 2 was repeated except that:

in step 1.1), the amount of carbon black used was 1.7kg, and the mass of DMAc used to disperse the carbon black was 15 kg;

in step 1.2), the average particle size of the silicon dioxide is 2 μm;

in the step 1.3), PAA-2 resin is added, and the addition amount is 290 g; the addition amount of the tetraethoxysilane is 6 g;

in step 2), the total amount of PMDA was 0.1996 mol.

Example 5

Example 2 was repeated except that:

in step 1.2), the average particle size of the silica is 10 μm, the amount of the silica is 2.5kg, and the mass of DMAc used for dispersing the silica is 14 kg;

in the step 1.3), PAA-3 resin is added, and the addition amount is 330 g; the adding amount of the tetraethoxysilane is 70 g;

in step 2), the total amount of PMDA was 0.199 mol.

Example 6

Example 1 was repeated except that:

the step 1) is carried out according to the following operations:

1.1) uniformly mixing 3.4kg of carbon black (primary particle size is 25nm) and 30kg of DMAc, shearing and dispersing by adopting a high-speed shearing machine (the rotating speed is 1000r/min, the dispersing time is 2 hours), and dispersing by adopting a ball mill (the rotating speed is 1500r/min, the ball milling time is 60 minutes) to obtain black dispersion liquid for later use;

1.2) uniformly mixing 0.8kg of titanium dioxide (with the average particle size of 6 mu m) and 8kg of DMAc, and placing the mixture in a high-speed shearing machine to shear and disperse for 4 hours at the rotating speed of 3000r/min to obtain white dispersion liquid for later use;

1.3) mixing the black dispersion liquid and the white dispersion liquid, placing the obtained mixed liquid in a high-speed shearing machine, adding 21g of n-butyl titanate, shearing and dispersing at the rotating speed of 1500r/min for 20h, then placing the mixed liquid in ultrasonic equipment for ultrasonic dispersion for 2h, finally adding 210g of PAA-4 resin, and performing ultrasonic dispersion for 1h to obtain the black filler dispersion liquid.

Example 7

Example 1 was repeated except that:

in the step 1.1), the primary particle size of the carbon black is 25nm, the using amount is 2.5kg, and the mass of DMAc for dispersing the carbon black is 23 kg;

in step 1.2), the amount of silicon dioxide used was 6.7kg, and the mass of DMAc used to disperse the silicon oxide was 38 kg;

in the step 1.3), PAA-5 resin is added, and the addition amount is 460 g; the amount of n-butyl titanate added was 74 g.

Example 8

Example 1 was repeated except that:

in the step 1.1), the primary particle size of the carbon black is 25 nm;

in step 1.2), the amount of silica used was 6.7kg and the mass of DMAc used to disperse the silica was 49 kg;

in the step 1.3), PAA-6 resin is added, and the addition amount is 550 g; the non-metal alkoxide is methyl orthosilicate, and the addition amount of the non-metal alkoxide is 22 g; the material added with the methyl orthosilicate is placed in an ultrasonic device for ultrasonic dispersion for 4 hours after being sheared and dispersed for 10 hours.

Example 9

Example 1 was repeated except that:

example 1 was repeated except that:

in the step 1.1), the primary particle size of the carbon black is 100nm, the using amount is 5.9kg, and the mass of DMAc for dispersing the carbon black is 43 kg;

in step 1.2), the average particle size of the silicon dioxide is 3 μm;

in the step 1.3), PAA-7 resin is added, and the addition amount is 500 g; the non-metal alkoxide is tetraethoxysilane, and the addition amount of the non-metal alkoxide is 500 g;

in step 2), the total amount of PMDA was 0.198 mol.

Example 10

Example 1 was repeated except that:

the step 1) is carried out according to the following operations:

1.1) uniformly mixing 2.5kg of carbon black (with primary particle size of 30nm) and 29kg of DMAc, shearing and dispersing by using a high-speed shearing machine (the rotating speed is 2000r/min, the dispersing time is 1.5h), and then placing in ultrasonic equipment for ultrasonic dispersion for 2h to obtain black dispersion liquid for later use;

1.2) uniformly mixing 3.4kg of titanium dioxide (with the average particle size of 4 mu m) and 19kg of DMAc, and placing the mixture in a high-speed shearing machine to shear and disperse for 4 hours at the rotating speed of 2500r/min to obtain white dispersion liquid for later use;

1.3) mixing the black dispersion liquid and the white dispersion liquid, placing the obtained mixed liquid into a high-speed shearing machine, adding 60g of n-butyl titanate, shearing and dispersing for 10h at the rotating speed of 2500r/min, then placing the mixed liquid into ultrasonic equipment for ultrasonic dispersion for 2h, finally adding 290g of PAA-1 resin, shearing and stirring for 3h at the rotating speed of 2500r/min, and obtaining the black filler dispersion liquid.

Comparative example 1

Example 1 was repeated except that:

in step 1.2), the amount of silica used was 9kg and the mass of DMAc used to disperse the silica was 50 kg.

Comparative example 2

Example 1 was repeated except that:

in step 1.3), the amount of n-butyl titanate added was 504 g.

Comparative example 3

Example 1 was repeated except that:

in step 2), the total amount of PMDA was 0.1999 mol.

Comparative example 4

Example 1 was repeated except that:

in step 1.3), the amount of n-butyl titanate added was 600 g.

Comparative example 5

Example 1 was repeated except that:

in step 1.3), the amount of PAA-1 resin added was 1260 g.

Comparative example 6

Example 1 was repeated except that:

in step 2), the total amount of PMDA was 0.1978 mol.

Comparative example 7

Example 1 was repeated except that:

in step 1.3), the amount of n-butyl titanate added was 7.65 g.

Comparative example 8

Example 1 was repeated except that:

in step 1.3), the amount of PAA-1 resin added was 75.6 g.

The basic parameters for preparing black matte polyimide films in the above examples and comparative examples are summarized in the following table 2.

Table 2:

the black matte polyimide films obtained in the above examples and comparative examples were measured for their properties, and the results are shown in table 3 below.

Table 3:

Claims

1. a preparation method of a low-pinhole-occurrence high-insulation matte black polyimide film comprises the following steps:

1) preparation of the black filler dispersion:

1.3) mixing the black dispersion liquid and the white dispersion liquid, carrying out shear dispersion and/or ultrasonic dispersion on the obtained mixed liquid, then adding non-metal alkoxide, carrying out shear dispersion and/or ultrasonic dispersion, then adding a polyamic acid resin solution, and carrying out shear dispersion and/or ultrasonic dispersion to obtain a black filler dispersion liquid; wherein, the non-metal alkoxide is one or the combination of more than two of tetrabutyl titanate, ethyl orthosilicate and methyl orthosilicate, and the addition amount of the non-metal alkoxide is 0.1 to 5 weight percent of the total amount of the carbon black and the flatting agent; the solid content of the polyamic acid resin solution is 17-22 wt%, and the adding amount of the polyamic acid resin solution is 1-9 wt% of the total using amount of the carbon black and the flatting agent;

2) in a polar aprotic solvent, the ratio of 1: adding aromatic diamine and aromatic dianhydride in a molar ratio of 0.990-0.998 to react to prepare polyamic acid resin solution, then adding black filler dispersion liquid, stirring uniformly, then adding or not adding a stabilizer, and stirring uniformly to obtain matt black polyamic acid resin solution; the stabilizer is triphenyl phosphate and/or triphenyl phosphite; the addition amount of the black filler dispersion liquid is controlled to be 2-7 wt% of the solid content of the polyamic acid resin solution, and the addition amount of the flatting agent is 1-8 wt% of the solid content of the polyamic acid resin solution;

2. The method of claim 1, wherein: in the step 1.1), the carbon black is put into a polar aprotic solvent, and is subjected to shearing dispersion, and then to homogenization treatment, grinding treatment or ultrasonic dispersion to obtain a black dispersion liquid.

3. The method of claim 2, wherein: in the step 1.1), the step of the method,

the shearing dispersion is carried out at the rotating speed of 1000-3000r/min, and the shearing dispersion time is more than or equal to 0.5 h;

the homogenization treatment is carried out under the condition that the pressure is less than or equal to 50MPa, and the homogenization time is more than or equal to 15 min;

the grinding treatment is carried out at the rotating speed of 1000-3000r/min, and the grinding time is more than or equal to 0.5 h;

the time of ultrasonic dispersion is more than or equal to 0.5 h.

4. The method of claim 1, wherein: in the step 1.2), the flatting agent is placed in a polar aprotic solvent for shearing and dispersion to obtain a white dispersion liquid.

5. The method of claim 4, wherein: in the step 1.2), the shearing dispersion is carried out at the rotating speed of 1000-3000r/min, and the shearing dispersion time is not less than 0.5 h.

6. The method of claim 1, wherein: in the step 1.3), the step of the method,

the shearing dispersion is carried out at the rotating speed of 1000-3000r/min, and the shearing dispersion time is more than or equal to 1 h;

the time of ultrasonic dispersion is more than or equal to 1 h.

7. The method of claim 1, wherein: in the step 1), the matting agent is one or the combination of any two or more of silicon dioxide, titanium dioxide and calcium hydrophosphate.

8. The production method according to any one of claims 1 to 7, characterized in that: in the step 2), the addition amount of the stabilizer is 0.5-2 wt% of the solid content of the polyamic acid resin solution.

9. A low pinhole occurrence high dielectric matte black polyimide film prepared by the method of any one of claims 1-8.