Heat-resistant High-impedance BM Photoresist Based on Copolymer-grafted Modified Carbon Black and Preparation Method

Abstract

The present invention relates to a heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black and a preparation method thereof, belonging to the technical field of photoresist materials. In the present invention, carbon black is oxidized and modified, then a chlorinating agent is added to chlorinate the oxidized carbon black, and a living controllable free radical is introduced on the surface of the chlorinated carbon black to graft a copolymer on the surface of the carbon black, and finally acrylic acid-co-imide graft copolymer surface-modified carbon black or methacrylic acid-co-imide graft copolymer surface-modified carbon black with strong heat resistance is obtained. The high-impedance BM photoresist prepared by using the modified carbon black can provide strong electrostatic and steric stabilization effects, and also improve the dispersion stability of carbon black in the resin; in addition, the grafted polyimide chain on the copolymer has strong temperature resistance and corrosion resistance. By using the graft copolymer surface-modified carbon black, a high-impedance BM photoresist with a high OD value, high insulation, excellent heat resistance, and high-precision pattern linearity can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoresist materials, and particularly relates to surface-modified carbon black and its preparation method, and a high-impedance and high-temperature-resistant BM photoresist and its preparation method. Background Art

[0002] 8K (7680×4320) is the highest resolution frequency that current digital video can reach, and an 8K screen is the highest-definition display carrier. This carrier provides a good display platform for high-definition movie cameras and is an essential means for displaying ultra-high-definition films. The color display of traditional liquid crystal displays (LCDs) is achieved through color filters. Among them, BM (Black Matrix) photoresist is the black matrix in the color filter, and its main function is to isolate the color photoresist to prevent color mixing. Another important function is to block light to achieve black display. However, due to the limitations of traditional technologies, its optical density (OD) value always remains at 2.8 - 3.5 / μm, which usually causes light leakage on the screen. However, with the rapid development of high-precision 8K display technologies, there is an urgent need for a higher density of black pigments in BM photoresist to prevent light leakage. At the same time, however, too high a pigment concentration easily weakens the insulation of the photoresist. In addition, BM photoresist prepared from ordinary unmodified carbon black is prone to failure due to its inability to withstand high temperatures (230 - 270°C) during curing, which ultimately leads to a reduction in its surface impedance and obvious peeling. Therefore, there is an urgent need for a new type of "high light-shielding, strong impedance, high-temperature-resistant" BM photoresist that can balance performance.

[0003] Carbon black is a commonly used black pigment in BM photoresist. It is composed of quasi-graphite structural units, and the arrangement between the quasi-graphite lamellae is relatively disordered. The specific surface area of carbon black aggregates is large, and there are abundant polar groups on the surface. The cohesive force between particles is very strong. Therefore, there are problems such as difficult dispersion and easy flocculation in the matrix, which affect the compatibility of carbon black particles and the physical and chemical properties of composite materials.

[0004] Currently, there are few reports on the method of surface modification of carbon black applied to BM photoresist, and the existing carbon black surface treatment technologies are difficult to simultaneously meet the requirements of BM photoresist for 8K displays in terms of high resolution, high optical density, high surface resistance, and strong heat resistance. In view of the above problems, we have proposed a new technical solution. Summary of the Invention

[0005] The present invention first oxidatively modifies untreated carbon black with an oxidant; then adds a chlorinating agent to chlorinate the oxidized carbon black, and introduces acrylic acid or methacrylic acid, an acid anhydride capable of forming a stable free radical, an initiator, and a catalyst on the surface of the chlorinated carbon black, and conducts graft copolymerization on the surface of the carbon black in one step for further treatment; after the reaction is successful, a polyimide resin is grafted onto the copolymer chain for the second time, and finally, acrylic acid - co - imide graft copolymer surface - modified carbon black or methacrylic acid - co - imide graft copolymer surface - modified carbon black is obtained. A photosensitive resin containing carboxyl groups, surface - modified carbon black, a photoinitiator, a polyfunctional monomer, and a fourth solvent are uniformly mixed to obtain a mixture, and then the mixture is further ground by a nano - grinder so that the particle size of the mixture is 50 - 80 nm, and a high - impedance BM photoresist is prepared.

[0006] The object of the present invention can be achieved by the following technical solutions:

[0007] A heat - resistant high - impedance BM photoresist based on copolymer - graft - modified carbon black comprises the following raw materials in parts by weight: 25 parts by weight of a photosensitive resin containing carboxyl groups, 20 - 30 parts by weight of acrylic polymer surface - modified carbon black, 0.1 - 3 parts by weight of a photoinitiator, 1 - 20 parts of a polyfunctional monomer, and 150 - 400 parts by weight of a fourth solvent.

[0008] As a preferred technical solution of the present invention, the photosensitive resin containing carboxyl groups is one of acrylic resin, epoxy - modified acrylic resin, polyester - modified acrylic resin, bisphenol fluorene - modified acrylic resin, polyurethane acrylate resin, silicone - modified acrylic resin, and polyamide - modified acrylic resin.

[0009] As a preferred technical solution of the present invention, the acrylic polymer surface - modified carbon black is acrylic acid - co - imide graft copolymer surface - modified carbon black or methacrylic acid - co - imide graft copolymer surface - modified carbon black, and the preparation method comprises the following steps:

[0010] S1. Under nitrogen protection, carbon black, an oxidant, and a first solvent are heated, stirred, and refluxed for 5 - 8 h, filtered, washed with deionized water until neutral, and then vacuum - dried to obtain oxidized carbon black;

[0011] S2. The oxidized carbon black, a chlorinating agent, and a second solvent are stirred and refluxed at 15 - 25 °C for 1 - 3 h. After removing the excess chlorinating agent and solvent by rotary evaporation, the second solvent, a first initiator, a copolymerization monomer, and a polymerization catalyst are added again, nitrogen is continuously introduced for 30 - 90 min, and then heated, stirred, and refluxed for 12 - 18 h. The slurry is filtered and vacuum - dried to obtain acrylic acid - co - acid anhydride copolymer surface - modified carbon black or methacrylic acid - co - acid anhydride copolymer surface - modified carbon black;

[0012] S3. Add acrylic acid - co - anhydride copolymer surface - modified carbon black or methacrylic acid - co - anhydride copolymer surface - modified carbon black, grafting resin, and acid - binding agent into a third solvent. After stirring and reacting at 40 - 60 °C for 1 - 3 h, filter the slurry and dry it under vacuum to obtain acrylic acid - co - imide graft copolymer surface - modified carbon black or methacrylic acid - co - imide graft copolymer surface - modified carbon black.

[0013] As a preferred technical solution of the present invention, the DBP oil absorption value of the carbon black in step S1 is 30 - 100 ml / 100 g, and the specific surface area is 30 - 150 m 2 / g; the oxidant is one of formaldehyde, hydrogen peroxide solution, sulfuric acid, nitric acid, acidic potassium permanganate solution, potassium dichromate solution, saturated potassium persulfate solution; the first solvent is one of anhydrous ethanol, methanol, ethyl acetate, dichloromethane.

[0014] As a preferred technical solution of the present invention, the chlorinating agent in step S2 is one of thionyl chloride, phosphorus trichloride, phosphorus pentachloride, sulfuryl chloride; the second solvent is one of tetrahydrofuran, methanol, toluene, xylene, dioxane, anisole, dimethyl sulfoxide, methanol, acetonitrile; the first initiator is one of 3 - hydroxy - 2,2 - dimethylpropyl 3 - hydroxy - 2,2 - dimethylpropionate of organic halide, 3 - (trichlorosilyl)propyl 2 - bromo - 2 - methylpropionate, 2 - bromo - N - [2 - (3,4 - dihydroxyphenyl)ethyl]propanamide; the comonomer includes a first comonomer and a second comonomer. The first comonomer is one of acrylic acid and methacrylic acid, and the second comonomer is an acid anhydride capable of forming a stable free radical, and its structure is one of Chemical General Formulas 1 and 2; the polymerization catalyst is one of copper salts such as copper bromide, cuprous bromide, iron bromide, iron chloride, ferric chloride hexahydrate.

[0015]

[0016] Among them, R1 and R2 respectively represent one of a hydrogen atom, a methyl group, a chlorine atom, a phenyl group, and a phosphorus heterocyclic group; R3 and R4 respectively represent one of a hydrogen atom, a methyl group, a chlorine atom, and a phenyl group.

[0017] As a preferred technical solution of the present invention, the grafting resin in step S3 is polyimide, and the structural formula is one of those shown in Chemical General Formulas 3 - 7; the acid - binding agent is one of 4 - dimethylaminopyrimidine, triethylamine, sodium carbonate, and potassium carbonate; the third solvent is one of N,N - dimethylformamide, tetrahydrofuran, N,N - dimethylacetamide, and N - methylpyrrolidone.

[0018]

[0019]

[0020] Among them, n is 300 to 800.

[0021] As a preferred technical solution of the present invention, the photoinitiator is one of a triazine compound, a biimidazole compound, an acetophenone compound, an oxime ester compound, a benzophenone compound, a thioxanthone compound, and a phosphine oxide compound.

[0022] As a preferred technical solution of the present invention, the multifunctional monomer is one of 1,6 - hexanediol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0023] As a preferred technical solution of the present invention, the fourth solvent is one of propylene glycol monomethyl ether acetate, ethyl lactate, propylene glycol monomethyl ether, ethyl 3 - ethoxypropionate, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 3 - methoxybutyl acetate, 3 - methoxy - 1 - butanol, 4 - hydroxy - 4 - methyl - 2 - pentanone, N,N - dimethylformamide, and N - methylpyrrolidone.

[0024] Furthermore, the preparation method of the heat - resistant high - impedance BM photoresist based on copolymer - grafted modified carbon black includes the following steps:

[0025] (1) Uniformly mix a carboxyl - containing photosensitive resin, acrylic polymer - surface - modified carbon black, a photoinitiator, a multifunctional monomer, and a fourth solvent to obtain a mixture;

[0026] (2) Further grind the mixture through a nano - grinder so that the particle size of the mixture is 50 - 80 nm, thereby obtaining the high - impedance BM photoresist.

[0027] Advantages of the present invention:

[0028] (1) The present invention provides a surface - modified carbon black. First, oxidize the surface of the carbon black with oxidants such as hydrogen peroxide solution and formaldehyde to increase the surface oxygen content and make the surface of the carbon black have abundant active hydrogens; then introduce living - controlled free radicals on the surface of the carbon black through an initiator to graft a copolymer on the surface of the carbon black; finally, utilize the active groups on the side chain of the copolymer to graft a polyimide chain with strong heat - resistant performance on the surface of the carbon black for the second time.

[0029] (2) The present invention also provides a high-impedance BM photoresist prepared by using surface-modified carbon black. In this high-impedance BM photoresist, the acrylic acid-co-acylimide or methacrylic acid-co-acylimide copolymer grafted on the surface of the carbon black can provide strong electrostatic and steric stabilization effects, improving the dispersion stability of the carbon black in the resin. In addition, the polyimide chains grafted on the copolymer have strong heat resistance and corrosion resistance, improving the heat resistance and chemical resistance of the carbon black during the resin curing process.

[0030] (3) By using surface-modified carbon black, the present invention can obtain a high-impedance BM photoresist with a high OD value, high insulation, excellent heat resistance, and high-precision pattern linearity. Detailed implementation manners

[0031] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following examples are provided to describe in detail the specific implementation manners, structures, features, and effects of the present invention.

[0032] The untreated carbon blacks in the following examples and comparative examples can be selected from PRINTEX-U, PRINTEX-V, PRINTEX-140U, PRINTEX-140V, PRINTEX-95, PRINTEX-85, PRINTEX-75, PRINTEX-55, PRINTEX-45, PRINTEX-300, PRINTEX-35, PRINTEX-25, PRINTEX-200, PRINTEX-40, PRINTEX-30, PRINTEX-3, PRINTEX-A, PRINTEX-BLACK-550, PRINTEX-BLACK-350, SPECIAL BLACK-250, SPECIAL BLACK-250, SPECIAL BLACK-100 and LAMP BLACK-101 of Orion Engineered Carbons GmbH; diagram blackⅡ, diagram black N339, diagram blackSH, diagram black H, diagram black LH, diagram black LA, diagram black SF, diagramblack N550M, diagram black M, diagram black E, diagram black G, diagram black R, diagram black N760M, diagram black LR, #2700, #2600, #2400, #2350, #2300, #2200, #1000, #980, #900, MCF88, #52, #50, #47, #45, #45L, #25, #CF9, #95, #3030, #3050, MA7, MA77, MA8 of Mitsubishi Heavy Industries, Ltd.RAVEN-1100ULTRA, RAVEN-1080ULTRA, RAVEN-1060ULTRA, RAVEN-1040, RAVEN-1035, RAVEN-1020, RAVEN-1000, RAVEN-890H, RAVEN-890, RAVEN-880ULTRA, RAVEN-860ULTRA, RAVEN-850, RAVEN-820, RAVEN-790ULTRA, RAVEN-780ULTRA, RAVEN-760ULTRA, RAVEN-520, RAVEN-500, RAVEN-460, RAVEN-450, RAVEN-430ULTRA, RAVEN-420, RAVEN-410, RAVEN-2500ULTRA, RAVEN-2000, RAVEN-1500, RAVEN-1255, RAVEN-1250, RAVEN-1200, RAVEN-1190ULTRA and RAVEN-1170 of Columbia Chemical Co., Ltd., USA; the photoinitiator can be selected from triazine compounds: 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s-triazine and 2-(3,4-dimethoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine, biimidazole compounds: 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyldiimidazole, 2,2'-di(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-diimidazole, acetophenone compounds: 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-(4-methylthiophenyl)-2-morpholinone and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, oxime ester compounds: 1-[4-(phenylthio)phenyl]-1,2-octanedione-2-(O-benzoyl oxime) and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyl oxime), benzophenone compounds: 4,4'-bis(dimethylamino)benzophenone and 4,4'-bis(diethylamino)benzophenone, thioxanthone compounds: 2,4-diethylthioxanthone, 2-chlorothioxanthone, isopropylthioxanthone and 2-isopropylthioxanthone, phosphine oxide compounds: 2,4,6-trimethylbenzoyl diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and bis(2,6-xylyl)phosphoryl chloride.;

[0033] Modification Example 1

[0034] Preparation of oxidized carbon black:

[0035] Take 300 g of carbon black PRINTEX-U and 5 L of 30% hydrogen peroxide solution into a three-necked flask equipped with a reflux condenser. Start the stirrer, heat to 65 °C and react for 6 h, then filter and dry at 100 °C to obtain oxidized carbon black.

[0036] Modification Example 2

[0037] Preparation of oxidized carbon black:

[0038] Take 300 g of carbon black PRINTEX-U and 3 L of 70% concentrated sulfuric acid into a three-necked flask equipped with a reflux condenser. Start the stirrer, heat to 65 °C and react for 6 h, then filter and dry at 100 °C to obtain oxidized carbon black.

[0039] Synthesis Examples 3-8

[0040] Preparation of acrylic polymer surface-modified carbon black:

[0041] First, take 30 parts by weight of oxidized carbon black, 196.56 parts by weight of chlorinating agent (thionyl chloride, hereinafter referred to as F-1), and 106.8 parts by weight of the second solvent (tetrahydrofuran, hereinafter referred to as THF) and add them to a three-necked flask equipped with a reflux condenser. Start the stirrer, stir and reflux at room temperature for 1 h. After the reaction is completed, rotary evaporation is used to remove the excess chlorinating agent and solvent. After drying, take 10 parts by weight of the first comonomer (acrylic acid, hereinafter referred to as AA), 11.8 parts by weight of the second comonomer (2,3-diphenylmaleic anhydride or cis-4-cyclohexene-1,2-dicarboxylic anhydride, hereinafter referred to as S-1 or S-2 respectively), 79.2 parts by weight of the first initiator 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropionate, hereinafter referred to as Br-1], and 1.34 parts by weight of polymerization catalyst (copper bromide, hereinafter referred to as C-1), and continuously introduce nitrogen for 30 min to displace the air in the bottle. Heat the reaction system to 60 °C and then start stirring and refluxing for at least 12 h. After the reaction is completed, filter the slurry. Acrylic-co-anhydride copolymer surface-modified carbon black is obtained.

[0042] Subsequently, the above-obtained acrylic acid-co-anhydride copolymer surface-modified carbon black, 20 parts by weight of graft resin (represented by Chemical Formulas 3 or 5 or 7 respectively, where n is 800, hereinafter simply referred to as X-1 or X-2 or X-3), 0.2 parts by weight of acid-binding agent (4-dimethylaminopyrimidine, hereinafter simply referred to as DAMP), and 60 parts by weight of the third solvent (N,N-dimethylformamide, hereinafter simply referred to as DMF) were added to a three-necked flask equipped with a reflux condenser. The stirrer was started, and the mixture was stirred and refluxed at 60 °C for 1 h, and the slurry was filtered. Finally, the acrylic polymer surface-modified carbon black in Synthesis Examples 3-8 was obtained by vacuum drying. The types and amounts of each raw material in Synthesis Examples 3-8 are shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] Control Example

[0047] In Control Example 9, unmodified carbon black PRINTEX-U was used instead of the acrylic polymer surface-modified carbon black; in Control Example 10, the oxidized carbon black in Modification Example 1 was used instead of the acrylic polymer surface-modified carbon black.

[0048] Preparation of the photoresist of Examples 11-18BM:

[0049] 20 parts by weight of the acrylic polymer surface-modified carbon black in Synthesis Examples 3-8 above, 25 parts by weight of bisphenol fluorene-modified acrylic resin (KBR-101, purchased from KISCO, Korea), 0.37 part by weight of photoinitiator 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyl-oxime) (hereinafter simply referred to as Y-1), 6.25 parts by weight of polyfunctional monomer (dipentaerythritol hexaacrylate, hereinafter referred to as DPHA), and 212.5 parts by weight of the fourth solvent (propylene glycol monomethyl ether acetate, hereinafter referred to as PGMEA) were respectively mixed and dispersed evenly to obtain uniform black mixtures, which were BM photoresists 11-16. Then, 20 parts by weight of the above Comparative Example 9 or Comparative Example 10, 25 parts by weight of bisphenol fluorene-modified acrylic resin (KBR-101, purchased from KISCO, Korea), 0.37 part by weight of photoinitiator 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyl-oxime) (hereinafter simply referred to as Y-1), 6.25 parts by weight of polyfunctional monomer (dipentaerythritol hexaacrylate, hereinafter referred to as DPHA), and 212.5 parts by weight of the fourth solvent (propylene glycol monomethyl ether acetate, hereinafter referred to as PGMEA) were respectively mixed and dispersed evenly to obtain uniform black mixtures, which were BM photoresist 17 or BM photoresist 18. Finally, the dispersibility of the photoresist was measured using a particle size analyzer (Zetasizepro, produced by Malvern). The types and amounts of the photoresist raw materials and the average particle size of the photoresist are shown in Table 2.

[0050] Table 2

[0051]

[0052]

[0053] Performance Evaluation

[0054] First, the solution particle size of the above-mentioned BM photoresists 11-18 of the examples was analyzed and characterized using a particle size analyzer; then they were evenly coated on the ITO-coated glass substrate by spin coating. After drying at 90 °C for 5 minutes, through a photomask with a pattern, exposure was carried out using an exposure machine with a 365 nm wavelength LED light source, and then, development was carried out with a 0.5 wt% Na2CO3 aqueous solution, and finally, thermal curing was carried out at 230 °C, 250 °C, and 270 °C for 30 minutes, respectively. The obtained coatings were used for the following evaluations.

[0055] (1) Surface resistance value

[0056] Use a high-resistance meter (6517B, produced by Keithley) with the 8009 fixture to measure the surface resistance values of each coating of BM photoresist 11-18 after curing at 230 °C, 250 °C, and 270 °C respectively under a voltage condition of 1000V (the results are shown in Table 3).

[0057] (2) OD value

[0058] Use a spectrophotometer (UV-2700, produced by Shimadzu Corporation) to measure the light transmittance of each substrate at 550 nm, and obtain the OD values of each coating of BM photoresist 11-18 after curing at 230 °C, 250 °C, and 270 °C (the results are shown in Table 3).

[0059] Table 3

[0060]

[0061]

[0062] As shown in the results of Table 3, the BM photoresist 11-16 formed by surface-modified carbon black with acrylic polymer has high resistance values and high OD values, and such properties remain stable under the high-temperature curing conditions of 230-270 °C. While the BM photoresist 17 and BM photoresist 18 formed by the control examples of unmodified carbon black and oxidized carbon black have lower resistance values and OD values, and their properties decrease significantly with the increase of curing temperature. The results show that the carbon black graft-modified by copolymer can significantly enhance its surface impedance, light-shielding property, and high-temperature resistance as a BM photoresist.

[0063] The above description is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or equivalent variations within the scope of the technical solution of the present invention by using the above-disclosed technical content. However, as long as it does not depart from the content of the technical solution of the present invention, any indirect modification, equivalent variation, and modification made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. Heat-resistant high-impedance BM photoresist based on copolymer-grafted carbon black, characterized in that: It comprises the following raw materials in parts by weight: 25 parts by weight of a carboxyl-containing photosensitive resin, 20 - 30 parts by weight of an acrylic polymer surface-modified carbon black, 0.1 - 3 parts by weight of a photoinitiator, 1 - 20 parts of a polyfunctional monomer, and 150 - 400 parts by weight of a fourth solvent; The acrylic polymer surface-modified carbon black is an acrylic-co-imide graft copolymer surface-modified carbon black or a methacrylic acid-co-imide graft copolymer surface-modified carbon black, and the preparation method comprises the following steps: S1. Under nitrogen protection, carbon black, an oxidant, and a first solvent are heated, stirred, and refluxed for 5 - 8 h, filtered, washed with deionized water until neutral, and then vacuum dried to obtain oxidized carbon black; S2. The oxidized carbon black, a chlorinating agent, and a second solvent are stirred and refluxed at 15 - 25 °C for 1 - 3 h. After removing the excess chlorinating agent and solvent by rotary evaporation, the second solvent, a first initiator, a comonomer, and a polymerization catalyst are added again. Nitrogen is continuously introduced for 30 - 90 min, and then heated, stirred, and refluxed for 12 - 18 h. The slurry is filtered and vacuum dried to obtain an acrylic-co-anhydride copolymer surface-modified carbon black or a methacrylic acid-co-anhydride graft copolymer surface-modified carbon black; S3. The acrylic-co-anhydride copolymer surface-modified carbon black or the methacrylic acid-co-anhydride graft copolymer surface-modified carbon black, a grafting resin, and an acid-binding agent are added to a third solvent, stirred and reacted at 40 - 60 °C for 1 - 3 h, the slurry is filtered, and vacuum dried to obtain an acrylic-co-imide graft copolymer surface-modified carbon black or a methacrylic acid-co-imide graft copolymer surface-modified carbon black.

2. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, wherein: The carboxyl-containing photosensitive resin is one of an acrylic resin, an epoxy-modified acrylic resin, a polyester-modified acrylic resin, a bisphenol fluorene-modified acrylic resin, a polyurethane acrylate resin, a silicone-modified acrylic resin, and a polyamide-modified acrylic resin.

3. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, wherein: The DBP oil absorption value of the carbon black described in step S1 is 30 to 100 ml / 100 g, and the specific surface area is 30 to 150 m 2 / g; the oxidizing agent is one of formaldehyde, hydrogen peroxide solution, sulfuric acid, nitric acid, acidic potassium permanganate solution, potassium dichromate solution, saturated potassium persulfate solution; the first solvent is one of anhydrous ethanol, methanol, ethyl acetate, dichloromethane.

4. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, characterized in that: The chlorinating agent in step S2 is one of thionyl chloride, phosphorus trichloride, phosphorus pentachloride, and sulfuryl chloride; the second solvent is one of tetrahydrofuran, methanol, toluene, xylene, dioxane, anisole, dimethyl sulfoxide, methanol, and acetonitrile; the first initiator is one of 3-hydroxy-2,2-dimethylpropyl 3-hydroxy-2,2-dimethylpropionate of an organic halide, 3-(trichlorosilyl)propyl 2-bromo-2-methylpropionate, and 2-bromo-N-[2-(3,4-dihydroxyphenyl)ethyl]propanamide; the comonomer includes a first comonomer and a second comonomer. The first comonomer is one of acrylic acid and methacrylic acid, and the second comonomer is an acid anhydride capable of forming a stable free radical, and its structure is one of chemical general formula 1 and chemical general formula 2; the polymerization catalyst is one of copper bromide, cuprous bromide, iron bromide, ferric chloride, and ferric chloride hexahydrate; wherein, R1 and R2 respectively represent one of a hydrogen atom, a methyl group, a chlorine atom, a phenyl group, and a phosphorous heterocyclic group; R3 and R4 respectively represent one of a hydrogen atom, a methyl group, a chlorine atom, and a phenyl group.

5. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, characterized in that: The grafting resin described in step S3 is polyimide, and the structural formula is one of those shown in chemical general formula 3-7; the acid-binding agent is one of 4-dimethylaminopyrimidine, triethylamine, sodium carbonate, and potassium carbonate; the third solvent is one of N,N-dimethylformamide, tetrahydrofuran, N,N-dimethylacetamide, and N-methylpyrrolidone; wherein, n is 300-800.

6. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, characterized in that: The photoinitiator is one of triazine compounds, biimidazole compounds, acetophenone compounds, oxime ester compounds, benzophenone compounds, thioxanthone compounds, and phosphine oxide compounds.

7. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, wherein: The polyfunctional monomer is one of 1,6-hexanediol diacrylate, ethylene glycol diacrylate, neopentyl glycol diacrylate, triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

8. The heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to claim 1, wherein: The fourth solvent is one of propylene glycol monomethyl ether acetate, ethyl lactate, propylene glycol monomethyl ether, ethyl 3-ethoxypropionate, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 3-methoxybutyl acetate, 3-methoxy-1-butanol, 4-hydroxy-4-methyl-2-pentanone, N,N-dimethylformamide, and N-methylpyrrolidone.

9. The preparation method of the heat-resistant high-impedance BM photoresist based on copolymer-grafted modified carbon black according to any one of claims 1-8, characterized in that: It includes the following steps: (1) Uniformly mix a carboxyl-containing photosensitive resin, acrylic polymer surface-modified carbon black, a photoinitiator, a polyfunctional monomer, and a fourth solvent to obtain a mixture; (2) Further grind the mixture through a nano-grinder so that the particle size of the mixture is 50-80 nm, thus obtaining a high-impedance BM photoresist.

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