Photoresist for capacitive touch sensor and preparation process thereof

Abstract

The invention relates to the technical field of photoresist, in particular to photoresist for a capacitive touch sensor and a preparation process of the photoresist. The invention discloses a preparation process of photoresist for a capacitive touch sensor. The preparation process comprises the following steps: preparing a modified photoreaction agent; preparing modified polyimide resin powder; preparing silicon dioxide hollow carbon spheres and nano titanium dioxide hybrid particles; and preparing the photoresist. The preparation method comprises the following steps: firstly carrying out nitration reaction on 4-tert-butylphenol, then reducing nitryl into amino to obtain amino substituted 4-tert-butylphenol, protecting the amino by di-tert-butyl dicarbonate ester, then oxidizing iodobenzene into a high-valence iodine active intermediate by taking m-chloroperoxybenzoic acid as an oxidizing agent, and reacting with Boc-amino substituted 4-tert-butylphenol to obtain the high-valence iodine-substituted 4-tert-butylphenol. And finally, carrying out a replacement reaction with silver trifluoromethanesulfonate, carrying out deprotection to obtain a modified photoreaction agent, and carrying out a condensation polymerization reaction on the modified photoreaction agent, 4, 4 '-hexafluoroisopropyl phthalic anhydride and the like to generate a polyamic acid prepolymer, so that the photoetching resolution can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of photoresist technology, specifically to a photoresist for capacitive touch sensors and its preparation process. Background Technology

[0002] As a core interactive component in consumer electronics, automotive displays, and smart wearable devices, capacitive touch sensors rely heavily on the comprehensive performance of the photoresist used in electrode processing for their touch sensitivity, signal stability, patterning accuracy, and long-term reliability. Polyimide photoresist, with its excellent heat resistance, mechanical strength, and dielectric stability, has become the preferred material for the fine pattern transfer of transparent conductive electrodes in capacitive touch sensors and is widely used in the manufacturing of high-precision touch devices.

[0003] However, existing polyimide photoresists mostly use rigid aromatic backbones as their core structure, resulting in poor molecular chain interface compatibility. They only have physical adsorption with the ITO transparent conductive layer, glass substrate, and metal mesh electrodes used in capacitive touch sensors, lacking stable chemical bonding support and exhibiting poor adhesion. In addition, the internal stress of the photoresist film after curing is relatively large, making it prone to interface failures such as film lifting, edge peeling, and pattern detachment during development, wet etching, high-temperature heat treatment, and damp heat aging processes. Currently, the adhesion performance is usually improved by additionally coating a silane coupling agent primer, which not only increases the process flow and production cost but also easily introduces impurities at the interface, interfering with the accuracy of the photolithographic pattern and dielectric stability. Moreover, traditional polyimide photoresists mostly use physically blended small-molecule photoacid generators. The photoacid generated after exposure is prone to random excessive diffusion during the heat drying process, causing the boundaries of the exposed area to become diffuse and the edges of the pattern to become blurred, resulting in low photolithographic resolution and making it difficult to meet the high-precision patterning requirements of micron-level narrow linewidth electrodes in capacitive touch sensors.

[0004] In addition, the dielectric constant of existing polyimide photoresists is generally too high. When applied to touch electrodes, it will significantly increase the parasitic capacitance between electrodes, interfere with the stable transmission of touch signals, reduce the response speed and positioning accuracy of the sensor, and make it difficult to meet the requirements of high-sensitivity touch interaction.

[0005] Therefore, there is a need to propose a photoresist for capacitive touch sensors with low dielectric constant, high resolution, and adhesion, as well as its fabrication process. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a photoresist for capacitive touch sensors and its fabrication process.

[0007] This invention provides a process for fabricating photoresist for capacitive touch sensors, comprising the following steps: S1: Preparation of modified photosensitive agent 4-tert-butylphenol was nitrated under strong acid catalysis, and then the nitro group was reduced to an amino group by hydrogen catalysis using a Pd / C catalyst. Then it was reacted with ditert-butyl dicarbonate, then with iodobenzene and m-chloroperoxybenzoic acid, and finally with silver trifluoromethanesulfonate. After deprotection by trifluoroacetic acid, a modified photosensitive agent was obtained. S2: Preparation of modified polyimide resin powder S2.1: Add the diamine mixture containing the above modified photosensitive agent to N-methylpyrrolidone at a ratio of 1g:(8-10)mL, and simultaneously add 0.05-0.1% of hydroquinone polymerization inhibitor by total mass of the diamine mixture. Stir under nitrogen protection until completely dissolved, cool to 0-5℃, and add 4,4'-hexafluoroisopropylphthalic anhydride in 6-7 portions, with an interval of 10-15min each time. Then remove the ice-water bath and stir the reaction at room temperature for 6-8h to obtain polyamic acid prepolymer. S2.2: Triethylamine was added to the above polyamic acid prepolymer, followed by N-phenylmaleimide. The mixture was stirred at room temperature for 3-4 hours, and then azobisisobutyronitrile was added. The mixture was heated and stirred at 65-75°C for 1-2 hours under nitrogen protection. The mixture was then poured into 4 times its volume of a 50% ethanol aqueous solution to precipitate the precipitate. The precipitate was collected by filtration and then washed with deionized water and anhydrous ethanol in sequence. The mixture was subjected to gradient thermal imidization and vacuum drying to obtain modified polyimide resin powder. S3: Preparation of silica hollow carbon spheres and nano-titanium dioxide hybrid particles Nano-silica was dispersed in deionized water, and resorcinol and formaldehyde were added to react. Then, a hydrothermal reaction was carried out, followed by etching with dilute hydrofluoric acid solution to prepare hollow carbon spheres of silica. Subsequently, nano-titanium dioxide was dispersed in buffer solution, and dopamine hydrochloride was added to react to obtain nano-titanium dioxide hybrid particles. S4: Preparation of photoresist The modified polyimide resin powder was added to a mixed solvent and heated and stirred at 50-60°C until completely dissolved. Then, the silica hollow carbon spheres and nano-titanium dioxide hybrid particles were added. After ultrasonic dispersion for 30-40 minutes, the mixture was filtered through a 0.2μm polytetrafluoroethylene filter membrane and vacuum degassed for 20-30 minutes to obtain the photoresist.

[0008] Furthermore, S1 includes the following steps: S1.1: Mix 4-tert-butylphenol, concentrated sulfuric acid, and glacial acetic acid in a ratio of (1.8-2.0) g: 1 mL: (7-9) mL and stir until completely dissolved. Cool to 0-2℃, add concentrated nitric acid (65 wt%) dropwise, stir for 1.5-2.5 h, pour into ice water and let stand to crystallize. Filter, wash with deionized water until neutral, and vacuum dry to obtain nitro-substituted 4-tert-butylphenol. The amount of concentrated nitric acid added is 3.5-4.5% of the volume of glacial acetic acid. S1.2: Add the above nitro-substituted 4-tert-butylphenol to anhydrous ethanol at a ratio of 1g:(10-12)mL, add a Pd / C catalyst with a palladium loading of 10wt%, introduce hydrogen to adjust the pressure to 0.1-0.2MPa, stir the reaction at 25-30℃ for 3-4h, filter to remove the catalyst, remove the solvent by rotary evaporation under reduced pressure to obtain amino-substituted 4-tert-butylphenol; S1.3: The above-mentioned amino-substituted 4-tert-butylphenol was added to anhydrous tetrahydrofuran at a ratio of 1g:(15-20)mL. After stirring and dissolving, di-tert-butyl dicarbonate and triethylamine were added. After stirring and reacting for 3-4 hours, the solvent was removed by rotary evaporation under reduced pressure, recrystallized and dried under vacuum to obtain Boc-amino-substituted 4-tert-butylphenol. The molar ratio of di-tert-butyl dicarbonate to amino-substituted 4-tert-butylphenol was (1.1-1.2):1, and the molar ratio of triethylamine to amino-substituted 4-tert-butylphenol was (1.2-1.3):1. S1.4: In a molar ratio of 1:(1.05-1.1):(1.1-1.2), the above Boc-amino-substituted 4-tert-butylphenol, iodobenzene and m-chloroperoxybenzoic acid were added to dichloromethane and stirred at 25-30℃ for 5-6 h. The precipitate was removed by filtration, and silver trifluoromethanesulfonate was added to the filtrate. The mixture was stirred for 1-2 h, filtered, concentrated under reduced pressure, recrystallized and dried under vacuum to obtain the precursor. The ratio of Boc-amino-substituted 4-tert-butylphenol to dichloromethane was 1 g:(13-15) mL. S1.5: Dissolve the above precursor in dichloromethane at a ratio of 1g:(10-15)mL, add trifluoroacetic acid dropwise at 1-3℃, and after the addition is complete, return to room temperature and stir for 2-3h. Then remove the solvent and trifluoroacetic acid by rotary evaporation under reduced pressure, and then obtain the modified photocatalytic agent by recrystallization and vacuum drying. The volume ratio of trifluoroacetic acid to precursor is 1:1.

[0009] Furthermore, S3 includes the following steps: S3.1: Add nano-silica to deionized water at a ratio of 1g:(30-40)mL, disperse ultrasonically for 30-40min, then add resorcinol and formaldehyde, adjust the pH to 8.0-8.5 with 0.1mol / L sodium hydroxide solution, stir and react at 25-30℃ for 4-5h, then hydrothermally react at 175-185℃ for 5.5-6.5h, collect the product by centrifugation after cooling, wash, vacuum dry, and then calcine at 800-850℃ for 2-3h under a nitrogen atmosphere to obtain silica core-shell particles; S3.2: Add the above silica core-shell particles to anhydrous ethanol at a ratio of 1g:(20-30)mL, disperse ultrasonically for 30-40min, then add a 2wt% dilute hydrofluoric acid solution, stir and etch for 10-15min, then add an equal volume of anhydrous ethanol to terminate the reaction, and then centrifuge, wash and vacuum dry to obtain silica hollow carbon spheres. The amount of dilute hydrofluoric acid solution added is 20-30% of the volume of anhydrous ethanol. S3.3: Add nano-titanium dioxide to buffer solution at a ratio of 1g:(40-50)mL, disperse by ultrasonication in an ice bath at 1-3℃ for 40-50min, remove the ice bath, add dopamine hydrochloride, stir and react at room temperature in the dark for 10-12h, collect the precipitate by centrifugation, wash with deionized water and anhydrous ethanol 3-4 times respectively, and vacuum dry to obtain nano-titanium dioxide hybrid particles.

[0010] Furthermore, the amount of Pd / C catalyst added is 2-3% of the mass of nitro-substituted 4-tert-butylphenol, and the molar ratio of silver trifluoromethanesulfonate to Boc-amino-substituted 4-tert-butylphenol is 1:(1-1.1).

[0011] Furthermore, the molar ratio of the mixture of 4,4'-hexafluoroisopropylphthalic anhydride and diamine is 1:(0.99-1.01), and the diamine mixture is composed of a modified photosensitive agent, 2,2'-bis(trifluoromethylbenzidine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and 3-aminostyrene in a molar ratio of (0.05-0.08):(0.6-0.7):(0.2-0.25):(0.03-0.05).

[0012] Furthermore, the amount of triethylamine is 1.1-1.2 times the molar amount of 3-aminostyrene, the amount of N-phenylmaleimide is 12-14% of the mass of 2,2'-bis(trifluoromethyl)benzidine, and the amount of azobisisobutyronitrile is 2.2-2.3% of the mass of N-phenylmaleimide.

[0013] Furthermore, the molar ratio of resorcinol to formaldehyde is 1:1.5, and the mass ratio of resorcinol to nano-silica is (2.8-3.2):1.

[0014] Furthermore, the buffer solution is a Tris-HCl buffer solution with a concentration of 0.01 mol / L and a pH of 6.5-7, and the amount of dopamine hydrochloride added is 10% of the mass of nano-titanium dioxide.

[0015] Furthermore, by mass percentage, the raw material composition of the photoresist is: 25-30% modified polyimide resin powder, 1.5-2% hollow carbon silica spheres, 0.5-1% nano-titanium dioxide hybrid particles, and the balance being a mixed solvent, wherein the mixed solvent consists of propylene glycol methyl ether acetate and γ-butyrolactone in a mass ratio of (4-5):1.

[0016] A photoresist for a capacitive touch sensor, which is prepared by the preparation process of a photoresist for a capacitive touch sensor described in any one of the above claims.

[0017] The present invention has the following advantages: 1. In this invention, 4-tert-butylphenol is first nitrated under strong acid catalysis, and then the nitro group is reduced to an amino group by hydrogen under Pd / C catalysis to obtain amino-substituted 4-tert-butylphenol. After the amino group is protected by di-tert-butyl dicarbonate, iodobenzene is oxidized to a high-valent iodine active intermediate using m-chloroperoxybenzoic acid as an oxidant. This intermediate reacts with Boc-amino-substituted 4-tert-butylphenol, and finally undergoes a displacement reaction with silver trifluoromethanesulfonate to deprotect it, resulting in a product that possesses both high-efficiency acid production capability under ultraviolet light and covalently resistant... The modified photoresist with bonded amino active sites undergoes a polycondensation reaction with 4,4'-hexafluoroisopropylphthalic anhydride to generate a polyamic acid prepolymer. The modified photoresist forms stable amide covalent bonds with the polyamic acid segments through amino groups, achieving covalent anchoring of the photoactive units on the polymer backbone. This fundamentally restricts the migration, aggregation, and precipitation of photosensitive components, creating a molecular-level confinement effect on photogenerated acids. It significantly suppresses the uncontrollable diffusion of acids during the heat treatment process after exposure, thereby greatly improving the lithography resolution.

[0018] 2. In this invention, a polyamic acid prepolymer is generated by first reacting a diamine mixture with a dianhydride through a polycondensation reaction. A flexible siloxane segment is then introduced into the main chain using 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Next, an addition reaction is performed between the vinyl groups on the side chains of the polyamic acid prepolymer and N-phenylmaleimide to introduce maleimide self-assembly adhesion groups into the side chains. Finally, the polyamic acid segments undergo thermal imidization to form a siloxane-containing main chain segment with maleimide-branched functionalized side chains. The photoresist, due to the siloxane bonds in its structure forming stable covalent bonds with the substrate surface, significantly releases the internal stress generated during curing, heat treatment, and processing of the photoresist. This fundamentally avoids the problems of film lifting, edge peeling, and pattern detachment caused by internal stress concentration in traditional rigid polyimides. The maleimide self-assembly groups can form strong coordination and covalent bonds with the active sites on the substrate surface, constructing a continuous adhesion structure from the resin body to the substrate interface, thereby effectively improving the adhesion of the photoresist.

[0019] 3. In this invention, modified polyimide resin powder is dissolved in a mixed solvent, and then hollow carbon silica spheres and nano-titanium dioxide hybrid particles are added to form a photoresist. The hollow carbon silica spheres, relying on their internal hollow cavity structure, introduce a large amount of low-dielectric-constant air phase, directly constructing low-dielectric-constant microregions in a physical manner, becoming the core component for reducing the dielectric constant of the system. The polydopamine layer coated on the surface of the nano-titanium dioxide hybrid particles can serve as an interfacial compatibility bridging layer, forming both hydrogen bonds and covalent bonds with the polyimide matrix, and... The interaction between the silicon dioxide hollow carbon spheres and the nano-titanium dioxide hybrid particles effectively solves the problems of easy agglomeration and poor interfacial bonding of single nanofillers. It fundamentally solves the phenomenon of local electric field concentration and enhanced interfacial polarization caused by particle agglomeration. When the two are used together, the silicon dioxide hollow carbon spheres are responsible for providing the low dielectric structure, while the nano-titanium dioxide hybrid particles are responsible for optimizing the dispersion state and suppressing the polarization effect. This achieves multiple suppressions of electronic polarization, atomic polarization and interfacial polarization, thereby synergistically reducing the dielectric constant of the photoresist and improving touch sensitivity and signal stability. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the fabrication process of the photoresist used in the capacitive touch sensor of this invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0022] Example 1: A fabrication process for photoresist used in a capacitive touch sensor, such as... Figure 1 As shown, it includes the following steps: S1: Preparation of modified photosensitive agent S1.1: Mix 4-tert-butylphenol, concentrated sulfuric acid, and glacial acetic acid at a ratio of 1.8 g: 1 mL: 7 mL and stir until completely dissolved. Cool to 0°C, add concentrated nitric acid (65 wt%) dropwise, stir and react for 1.5 h, pour into ice water and let stand to crystallize. Filter, wash with deionized water until neutral, and vacuum dry to obtain nitro-substituted 4-tert-butylphenol. The amount of concentrated nitric acid added is 3.5% of the volume of glacial acetic acid. S1.2: The above-mentioned nitro-substituted 4-tert-butylphenol was added to anhydrous ethanol at a ratio of 1g:10mL, and a Pd / C catalyst with a palladium loading of 10wt% was added. Hydrogen gas was introduced to adjust the pressure to 0.1MPa, and the reaction was stirred at 25℃ for 3h. The catalyst was removed by filtration, and the solvent was removed by rotary evaporation under reduced pressure to obtain amino-substituted 4-tert-butylphenol. The amount of Pd / C catalyst added was 2% of the mass of nitro-substituted 4-tert-butylphenol. S1.3: The above-mentioned amino-substituted 4-tert-butylphenol was added to anhydrous tetrahydrofuran at a ratio of 1 g: 15 mL. After stirring and dissolving, di-tert-butyl dicarbonate and triethylamine were added. After stirring and reacting for 3 h, the solvent was removed by rotary evaporation under reduced pressure, recrystallized and dried under vacuum to obtain Boc-amino-substituted 4-tert-butylphenol, wherein the molar ratio of di-tert-butyl dicarbonate to amino-substituted 4-tert-butylphenol was 1.1:1 and the molar ratio of triethylamine to amino-substituted 4-tert-butylphenol was 1.2:1. S1.4: The above Boc-amino-substituted 4-tert-butylphenol, iodobenzene and m-chloroperoxybenzoic acid were added to dichloromethane at a molar ratio of 1:1.05:1.1. The mixture was stirred at 25°C for 5 h, the precipitate was removed by filtration, silver trifluoromethanesulfonate was added to the filtrate, and stirring was continued for 1 h. The mixture was then filtered, concentrated under reduced pressure, recrystallized and dried under vacuum to obtain the precursor. The molar ratio of Boc-amino-substituted 4-tert-butylphenol to dichloromethane was 1 g: 13 mL, and the molar ratio of silver trifluoromethanesulfonate to Boc-amino-substituted 4-tert-butylphenol was 1:1. S1.5: Dissolve the above precursor in dichloromethane at a ratio of 1g:10mL, add trifluoroacetic acid dropwise at 1℃, and after the addition is complete, return to room temperature and stir for 2h. Then remove the solvent and trifluoroacetic acid by rotary evaporation under reduced pressure, and then obtain the modified photocatalytic agent by recrystallization and vacuum drying. The volume ratio of trifluoroacetic acid to precursor is 1:1. S2: Preparation of modified polyimide resin powder S2.1: Add the diamine mixture to N-methylpyrrolidone at a ratio of 1g:8mL, and simultaneously add 0.05% of hydroquinone polymerization inhibitor by mass of the total diamine mixture. Stir under nitrogen protection until completely dissolved, cool to 0℃, and add 4,4'-hexafluoroisopropylphthalic anhydride in 6 portions, with an interval of 10min each time. Then remove the ice-water bath and stir at room temperature for 6h to obtain polyamic acid prepolymer. The molar ratio of 4,4'-hexafluoroisopropylphthalic anhydride to the diamine mixture is 1:0.99, and the diamine mixture is composed of modified photosensitive agent, 2,2'-bis(3-aminopropyl)tetramethyldisiloxane, and 3-aminostyrene in a molar ratio of 0.05:0.6:0.2:0.03. S2.2: Triethylamine and N-phenylmaleimide were added to the above polyamic acid prepolymer, and the mixture was stirred at room temperature for 3 hours. Then, azobisisobutyronitrile was added, and the mixture was heated and stirred at 65°C for 1 hour under nitrogen protection. Subsequently, the mixture was poured into 4 times its volume of a 50% ethanol aqueous solution, and a precipitate was formed. The precipitate was collected by filtration and washed with deionized water and anhydrous ethanol in sequence. Then, the mixture was heated at 80°C for 1 hour, 150°C for 1 hour, and 220°C for 1 hour in sequence for gradient thermal imidization. Finally, the mixture was dried under vacuum to obtain modified polyimide resin powder. The amount of triethylamine was 1.1 times the molar amount of 3-aminostyrene, the amount of N-phenylmaleimide was 12% of the mass of 2,2'-bis(trifluoromethyl)benzidine, and the amount of azobisisobutyronitrile was 2.2% of the mass of N-phenylmaleimide. S3: Preparation of silica hollow carbon spheres and nano-titanium dioxide hybrid particles S3.1: Add nano-silica to deionized water at a ratio of 1g:30mL, disperse ultrasonically for 30min, then add resorcinol and formaldehyde, adjust the pH to 8.0 with 0.1mol / L sodium hydroxide solution, stir and react at 25℃ for 4h, then hydrothermally react at 175℃ for 5.5h, cool, centrifuge to collect the product, wash, vacuum dry, and then calcine at 800℃ for 2h under a nitrogen atmosphere to obtain silica core-shell particles, wherein the molar ratio of resorcinol to formaldehyde is 1:1.5, and the mass ratio of resorcinol to nano-silica is 2.8:1; S3.2: The above-mentioned silica core-shell particles were added to anhydrous ethanol at a ratio of 1g:20mL, ultrasonically dispersed for 30min, then a 2wt% dilute hydrofluoric acid solution was added, and the mixture was stirred and etched for 10min. The reaction was then terminated by adding an equal volume of anhydrous ethanol to the dilute hydrofluoric acid solution. After centrifugation, washing, and vacuum drying, hollow silica carbon spheres were obtained. The amount of dilute hydrofluoric acid solution added was 20% of the volume of anhydrous ethanol. S3.3: Add nano-titanium dioxide to buffer solution at a ratio of 1g:40mL, sonicate in an ice bath at 1℃ for 40min, remove the ice bath, add dopamine hydrochloride, stir and react at room temperature in the dark for 10h, collect the precipitate by centrifugation, wash three times with deionized water and anhydrous ethanol respectively, and vacuum dry to obtain nano-titanium dioxide hybrid particles. The buffer solution is a 0.01mol / L Tris-HCl buffer solution with a pH of 6.5, and the amount of dopamine hydrochloride added is 10% of the mass of nano-titanium dioxide. S4: Preparation of photoresist The modified polyimide resin powder was added to the mixed solvent and heated and stirred at 50°C until completely dissolved. Then, the silica hollow carbon spheres and nano-titanium dioxide hybrid particles were added, and the mixture was ultrasonically dispersed for 30 min. After filtration through a 0.2 μm polytetrafluoroethylene filter membrane and vacuum degassing for 20 min, the photoresist was obtained. The photoresist was composed of the following raw materials by mass percentage: 25% modified polyimide resin powder, 1.5% silica hollow carbon spheres, 0.5% nano-titanium dioxide hybrid particles, and 73% mixed solvent. The mixed solvent consisted of propylene glycol methyl ether acetate and γ-butyrolactone in a mass ratio of 4:1.

[0023] Example 2: A fabrication process for photoresist used in a capacitive touch sensor, such as... Figure 1 As shown, it includes the following steps: S1.1: Mix 4-tert-butylphenol, concentrated sulfuric acid, and glacial acetic acid at a ratio of 1.9g:1mL:8mL and stir until completely dissolved. Cool to 1°C, add concentrated nitric acid (65wt%) dropwise, stir for 2 hours, pour into ice water and let stand to crystallize. Filter, wash with deionized water until neutral, and vacuum dry to obtain nitro-substituted 4-tert-butylphenol. The amount of concentrated nitric acid added is 4% of the volume of glacial acetic acid. S1.2: The above-mentioned nitro-substituted 4-tert-butylphenol was added to anhydrous ethanol at a ratio of 1g:11mL, and a Pd / C catalyst with a palladium loading of 10wt% was added. Hydrogen gas was introduced to adjust the pressure to 0.15MPa, and the reaction was stirred at 27.5℃ for 3.5h. The catalyst was removed by filtration, and the solvent was removed by rotary evaporation under reduced pressure to obtain amino-substituted 4-tert-butylphenol. The amount of Pd / C catalyst added was 2.5% of the mass of the nitro-substituted 4-tert-butylphenol. S1.3: The above-mentioned amino-substituted 4-tert-butylphenol was added to anhydrous tetrahydrofuran at a ratio of 1g:17.5mL. After stirring and dissolving, di-tert-butyl dicarbonate and triethylamine were added. After stirring and reacting for 3.5h, the solvent was removed by rotary evaporation under reduced pressure, recrystallized and dried under vacuum to obtain Boc-amino-substituted 4-tert-butylphenol, wherein the molar ratio of di-tert-butyl dicarbonate to amino-substituted 4-tert-butylphenol was 1.15:1 and the molar ratio of triethylamine to amino-substituted 4-tert-butylphenol was 1.25:1. S1.4: The above Boc-amino-substituted 4-tert-butylphenol, iodobenzene, and m-chloroperoxybenzoic acid were added to dichloromethane at a molar ratio of 1:1.075:1.15. The mixture was stirred at 27.5°C for 5.5 h, and the precipitate was removed by filtration. Silver trifluoromethanesulfonate was added to the filtrate, and the mixture was stirred for another 1.5 h. The mixture was then filtered, concentrated under reduced pressure, recrystallized, and dried under vacuum to obtain the precursor. The molar ratio of Boc-amino-substituted 4-tert-butylphenol to dichloromethane was 1 g:14 mL, and the molar ratio of silver trifluoromethanesulfonate to Boc-amino-substituted 4-tert-butylphenol was 1:1.05. S1.5: Dissolve the above precursor in dichloromethane at a ratio of 1g:12.5mL, add trifluoroacetic acid dropwise at 2℃, and after the addition is complete, return to room temperature and stir for 2.5h. Then remove the solvent and trifluoroacetic acid by rotary evaporation under reduced pressure, and then obtain the modified photocatalytic agent by recrystallization and vacuum drying. The volume ratio of trifluoroacetic acid to precursor is 1:1. S2: Preparation of modified polyimide resin powder S2.1: Add the diamine mixture to N-methylpyrrolidone at a ratio of 1g:9mL, and simultaneously add 0.075% of hydroquinone polymerization inhibitor by mass of the total diamine mixture. Stir under nitrogen protection until completely dissolved, cool to 3℃, and add 4,4'-hexafluoroisopropylphthalic anhydride in 6 portions, with an interval of 12.5min between each addition. Then remove the ice-water bath and stir at room temperature for 7h to obtain a polyamic acid prepolymer. The molar ratio of 4,4'-hexafluoroisopropylphthalic anhydride to the diamine mixture is 1:1, and the diamine mixture consists of a modified photosensitive agent, 2,2'-bis(trifluoromethylbenzidine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and 3-aminostyrene in a molar ratio of 0.065:0.65:0.225:0.04. S2.2: Triethylamine and N-phenylmaleimide were added to the above polyamic acid prepolymer, and the mixture was stirred at room temperature for 3.5 h. Then, azobisisobutyronitrile was added, and the mixture was heated and stirred at 70 °C for 1.5 h under nitrogen protection. Subsequently, the mixture was poured into 4 times its volume of a 50% ethanol aqueous solution, and a precipitate was formed. The precipitate was collected by filtration and then washed with deionized water and anhydrous ethanol in sequence. Then, the mixture was heated at 80 °C for 1 h, 150 °C for 1 h, and 220 °C for 1 h in sequence for gradient thermal imidization. Finally, the mixture was dried under vacuum to obtain modified polyimide resin powder. The amount of triethylamine was 1.15 times the molar amount of 3-aminostyrene, the amount of N-phenylmaleimide was 13% of the mass of 2,2'-bis(trifluoromethyl)benzidine, and the amount of azobisisobutyronitrile was 2.25% of the mass of N-phenylmaleimide. S3: Preparation of silica hollow carbon spheres and nano-titanium dioxide hybrid particles S3.1: Add nano-silica to deionized water at a ratio of 1g:35mL, disperse ultrasonically for 35min, then add resorcinol and formaldehyde, adjust the pH to 8.0 with 0.1mol / L sodium hydroxide solution, stir and react at 27.5℃ for 4.5h, then hydrothermally react at 180℃ for 6h, cool, centrifuge to collect the product, wash, vacuum dry, and then calcine at 825℃ for 2.5h under a nitrogen atmosphere to obtain silica core-shell particles, wherein the molar ratio of resorcinol to formaldehyde is 1:1.5, and the mass ratio of resorcinol to nano-silica is 3:1; S3.2: The above-mentioned silica core-shell particles were added to anhydrous ethanol at a ratio of 1g:25mL, ultrasonically dispersed for 35min, then a 2wt% dilute hydrofluoric acid solution was added, and the mixture was stirred and etched for 12.5min. The reaction was then terminated by adding an equal volume of anhydrous ethanol to the dilute hydrofluoric acid solution. After centrifugation, washing, and vacuum drying, hollow silica carbon spheres were obtained. The amount of dilute hydrofluoric acid solution added was 25% of the volume of anhydrous ethanol. S3.3: Add nano-titanium dioxide to buffer solution at a ratio of 1 g: 45 mL, sonicate at 2°C in an ice bath for 45 min, remove the ice bath, add dopamine hydrochloride, stir and react at room temperature in the dark for 11 h, collect the precipitate by centrifugation, wash three times with deionized water and anhydrous ethanol respectively, and vacuum dry to obtain nano-titanium dioxide hybrid particles. The buffer solution is a 0.01 mol / L Tris-HCl buffer solution with a pH of 6.5, and the amount of dopamine hydrochloride added is 10% of the mass of nano-titanium dioxide. S4: Preparation of photoresist The modified polyimide resin powder was added to a mixed solvent and heated and stirred at 55°C until completely dissolved. Then, the silica hollow carbon spheres and nano-titanium dioxide hybrid particles were added, and the mixture was ultrasonically dispersed for 35 min. After filtration through a 0.2 μm polytetrafluoroethylene filter membrane and vacuum degassing for 25 min, the photoresist was obtained. The photoresist was composed of the following raw materials by mass percentage: 27.5% modified polyimide resin powder, 1.75% silica hollow carbon spheres, 0.75% nano-titanium dioxide hybrid particles, and 70% mixed solvent. The mixed solvent consisted of propylene glycol methyl ether acetate and γ-butyrolactone in a mass ratio of 4.5:1.

[0024] Example 3: A fabrication process for photoresist used in a capacitive touch sensor, such as... Figure 1 As shown, it includes the following steps: S1.1: Mix 4-tert-butylphenol, concentrated sulfuric acid, and glacial acetic acid at a ratio of 2.0 g: 1 mL: 9 mL and stir until completely dissolved. Cool to 2°C, add concentrated nitric acid (65 wt%) dropwise, stir and react for 2.5 h, pour into ice water and let stand to crystallize, filter, wash with deionized water until neutral, and vacuum dry to obtain nitro-substituted 4-tert-butylphenol. The amount of concentrated nitric acid added is 4.5% of the volume of glacial acetic acid. S1.2: The above-mentioned nitro-substituted 4-tert-butylphenol was added to anhydrous ethanol at a ratio of 1g:12mL, and a Pd / C catalyst with a palladium loading of 10wt% was added. Hydrogen gas was introduced to adjust the pressure to 0.2MPa, and the reaction was stirred at 30℃ for 4h. The catalyst was removed by filtration, and the solvent was removed by rotary evaporation under reduced pressure to obtain amino-substituted 4-tert-butylphenol. The amount of Pd / C catalyst added was 3% of the mass of nitro-substituted 4-tert-butylphenol. S1.3: The above-mentioned amino-substituted 4-tert-butylphenol was added to anhydrous tetrahydrofuran at a ratio of 1 g: 20 mL. After stirring and dissolving, di-tert-butyl dicarbonate and triethylamine were added. After stirring and reacting for 4 h, the solvent was removed by rotary evaporation under reduced pressure, recrystallized and dried under vacuum to obtain Boc-amino-substituted 4-tert-butylphenol, wherein the molar ratio of di-tert-butyl dicarbonate to amino-substituted 4-tert-butylphenol was 1.2:1 and the molar ratio of triethylamine to amino-substituted 4-tert-butylphenol was 1.3:1. S1.4: The above Boc-amino-substituted 4-tert-butylphenol, iodobenzene, and m-chloroperoxybenzoic acid were added to dichloromethane in a molar ratio of 1:1.1:1.2. The mixture was stirred at 30°C for 6 hours, and the precipitate was removed by filtration. Silver trifluoromethanesulfonate was added to the filtrate, and the mixture was stirred for another 2 hours. The mixture was then filtered, concentrated under reduced pressure, recrystallized, and dried under vacuum to obtain the precursor. The molar ratio of Boc-amino-substituted 4-tert-butylphenol to dichloromethane was 1 g: 15 mL, and the molar ratio of silver trifluoromethanesulfonate to Boc-amino-substituted 4-tert-butylphenol was 1:1.1. S1.5: Dissolve the above precursor in dichloromethane at a ratio of 1g:15mL, add trifluoroacetic acid dropwise at 3℃, and after the addition is complete, return to room temperature and stir for 3h. Then remove the solvent and trifluoroacetic acid by rotary evaporation under reduced pressure, and then obtain the modified photocatalytic agent by recrystallization and vacuum drying. The volume ratio of trifluoroacetic acid to precursor is 1:1. S2: Preparation of modified polyimide resin powder S2.1: Add the diamine mixture to N-methylpyrrolidone at a ratio of 1g:10mL, and simultaneously add 0.1% hydroquinone polymerization inhibitor by mass of the total diamine mixture. Stir under nitrogen protection until completely dissolved, cool to 5℃, and add 4,4'-hexafluoroisopropylphthalic anhydride in 7 portions, with an interval of 15min between each addition. Then remove the ice-water bath and stir at room temperature for 8h to obtain a polyamic acid prepolymer. The molar ratio of 4,4'-hexafluoroisopropylphthalic anhydride to the diamine mixture is 1:1.01, and the diamine mixture consists of a modified photosensitive agent, 2,2'-bis(3-aminopropyl)tetramethyldisiloxane, and 3-aminostyrene in a molar ratio of 0.08:0.7:0.25:0.05. S2.2: Triethylamine and N-phenylmaleimide were added to the above polyamic acid prepolymer, and the mixture was stirred at room temperature for 4 hours. Then, azobisisobutyronitrile was added, and the mixture was heated and stirred at 75°C for 2 hours under nitrogen protection. Subsequently, the mixture was poured into 4 times its volume of a 50% ethanol aqueous solution, and a precipitate was formed. The precipitate was collected by filtration and then washed with deionized water and anhydrous ethanol in sequence. Then, the mixture was heated at 80°C for 1 hour, 150°C for 1 hour, and 220°C for 1 hour in sequence to carry out gradient thermal imidization. Finally, the mixture was dried under vacuum to obtain modified polyimide resin powder. The amount of triethylamine was 1.2 times the molar amount of 3-aminostyrene, the amount of N-phenylmaleimide was 14% of the mass of 2,2'-bis(trifluoromethyl)benzidine, and the amount of azobisisobutyronitrile was 2.3% of the mass of N-phenylmaleimide. S3: Preparation of silica hollow carbon spheres and nano-titanium dioxide hybrid particles S3.1: Nano-silica was added to deionized water at a ratio of 1 g: 40 mL, ultrasonically dispersed for 40 min, then resorcinol and formaldehyde were added. The pH was adjusted to 8.5 with 0.1 mol / L sodium hydroxide solution, and the mixture was stirred at 30 °C for 5 h, followed by hydrothermal reaction at 185 °C for 6.5 h. After cooling, the product was collected by centrifugation, washed, vacuum dried, and then calcined at 850 °C for 3 h under a nitrogen atmosphere to obtain silica core-shell particles. The molar ratio of resorcinol to formaldehyde was 1:1.5, and the mass ratio of resorcinol to nano-silica was 3.2:1. S3.2: The above-mentioned silica core-shell particles were added to anhydrous ethanol at a ratio of 1g:30mL, ultrasonically dispersed for 40min, then a 2wt% dilute hydrofluoric acid solution was added, and the mixture was stirred and etched for 15min. The reaction was then terminated by adding an equal volume of anhydrous ethanol to the dilute hydrofluoric acid solution. After centrifugation, washing, and vacuum drying, hollow silica carbon spheres were obtained. The amount of dilute hydrofluoric acid solution added was 30% of the volume of anhydrous ethanol. S3.3: Add nano-titanium dioxide to buffer solution at a ratio of 1g:50mL, sonicate in an ice bath at 3℃ for 50min, remove the ice bath, add dopamine hydrochloride, stir and react at room temperature in the dark for 12h, collect the precipitate by centrifugation, wash four times with deionized water and anhydrous ethanol respectively, and vacuum dry to obtain nano-titanium dioxide hybrid particles. The buffer solution is a 0.01mol / L Tris-HCl buffer solution with a pH of 7, and the amount of dopamine hydrochloride added is 10% of the mass of nano-titanium dioxide. S4: Preparation of photoresist The modified polyimide resin powder was added to a mixed solvent and heated and stirred at 60°C until completely dissolved. Then, the silica hollow carbon spheres and nano-titanium dioxide hybrid particles were added, and the mixture was ultrasonically dispersed for 40 minutes. After filtration through a 0.2 μm polytetrafluoroethylene filter membrane and vacuum degassing for 30 minutes, the photoresist was obtained. The raw material composition of the photoresist, by mass percentage, is as follows: The mixture comprises 30% modified polyimide resin powder, 2% silica hollow carbon spheres, 1% nano-titanium dioxide hybrid particles, and 67% mixed solvent, wherein the mixed solvent consists of propylene glycol methyl ether acetate and γ-butyrolactone in a mass ratio of 5:1.

[0025] Comparative Example 1 differs from Example 1 in that step S1 is removed and the modified photoreactive agent in step S2.1 is replaced with an equal amount of bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate.

[0026] Comparative Example 2 differs from Example 1 in that 1,3-bis(3-aminopropyl)tetramethyldisiloxane in step S2.1 and N-phenylmaleimide in step S2.2 are removed.

[0027] Comparative Example 3 differs from Example 1 in that 1,3-bis(3-aminopropyl)tetramethyldisiloxane is removed in step S2.1.

[0028] Comparative Example 4 differs from Example 1 in that N-phenylmaleimide in step S2.2 is removed.

[0029] Comparative Example 5 differs from Example 1 in that the hollow carbon silica spheres in step S4 are replaced with an equal amount of nano-titanium dioxide hybrid particles.

[0030] Comparative Example 6 differs from Example 1 in that step S3.2 is removed, and the hollow carbon silica spheres in step S4 are replaced with an equal amount of silica core-shell particles obtained in step S3.1.

[0031] Comparative Example 7 differs from Example 1 in that the nano-titanium dioxide hybrid particles in step S4 are replaced with an equal amount of hollow carbon spheres made of silicon dioxide.

[0032] Comparative Example 8 differs from Example 1 in that the nano-titanium dioxide hybrid particles in step S4 are replaced with an equal amount of nano-titanium dioxide.

[0033] Test example: Test 1: The photoresists prepared in Examples 1-3 and Comparative Example 1 were spin-coated onto silicon wafers. After vacuum drying, they were baked at 110°C for 90 seconds to form a photoresist coating with a thickness of approximately 1.5 μm. The photoresist coating was then exposed using a photolithography machine, developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution for 60 seconds, rinsed with deionized water, and dried with nitrogen to form a photoresist pattern. The photoresist pattern was then observed using a scanning electron microscope, and the minimum resolvable linewidth was recorded as the minimum resolution. The test was repeated three times, and the average value of the results is shown in Table 1.

[0034] Table 1: Test Results of Minimum Resolution of Photoresist Minimum resolution (μm) Example 1 1.8 Example 2 1.7 Example 3 1.5 Comparative Example 1 5 As shown in Table 1, in Comparative Example 1, the minimum resolution of the photoresist obtained by directly physically mixing bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate into the photoresist was significantly lower than that in Example 1. This demonstrates that by first nitrifying 4-tert-butylphenol under strong acid catalysis, and then reducing the nitro group to an amino group under Pd / C catalysis using hydrogen, amino-substituted 4-tert-butylphenol is obtained. After protecting the amino group with ditert-butyl dicarbonate, iodobenzene is oxidized to a high-valent iodine reactive intermediate using m-chloroperoxybenzoic acid as an oxidant. This intermediate reacts with Boc-amino-substituted 4-tert-butylphenol, and finally reacts with silver trifluoromethanesulfonate. By altering the reaction and removing protection, a modified photoresist with both high-efficiency acid-generating capability under ultraviolet light and covalently bondable amino active sites is obtained. After undergoing a polycondensation reaction with 4,4'-hexafluoroisopropylphthalic anhydride to generate a polyamic acid prepolymer, the modified photoresist forms stable amide covalent bonds with the polyamic acid segments through amino groups, achieving covalent anchoring of the photoactive units on the polymer backbone. This can fundamentally limit the migration, aggregation, and precipitation of photosensitive components, forming a molecular-level confinement effect on photogenerated acids, significantly suppressing the uncontrollable diffusion of acids during the heat-drying process after exposure, thereby greatly improving the lithography resolution.

[0035] Test 2: The photoresists prepared in Examples 1-3 and Comparative Examples 2-4 were spin-coated onto silicon wafers, baked and cured to form a coating with a thickness of 1.5 μm. The adhesion of the coating was tested according to GB / T 9286-1998, and the tape peeling rating was set from 0 to 5 (0 being the best and 5 being the worst). The results are shown in Table 2.

[0036] Table 2: Results of Photoresist Adhesion Test Adhesion level Example 1 Level 0 Example 2 Level 0 Example 3 Level 0 Comparative Example 2 Level 3 Comparative Example 3 Level 2 Comparative Example 4 Level 1 As shown in Table 2, in Comparative Example 2, without the addition of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and N-phenylmaleimide, the adhesion of the photoresist was significantly lower than that of Example 1. In Comparative Example 3, without the addition of 1,3-bis(3-aminopropyl)tetramethyldisiloxane, the adhesion of the photoresist was higher than that of Comparative Example 2, but still lower than that of Example 1. In Comparative Example 4, without the addition of N-phenylmaleimide, the adhesion of the photoresist was higher than that of Comparative Examples 2 and 3, but still lower than that of Example 1. Therefore, it can be seen that... First, a mixture of diamines and dianhydrides undergoes a polycondensation reaction to generate a polyamic acid prepolymer. Flexible siloxane segments are introduced into the main chain using 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Then, vinyl groups on the side chains of the polyamic acid prepolymer undergo an addition reaction with N-phenylmaleimide to introduce maleimide self-assembled adhesion groups into the side chains. Finally, the polyamic acid segments are thermally imidized to form a functionalized modified polyimide resin with siloxane segments in the main chain and maleimide-branched side chains, which can effectively improve the adhesion of photoresist.

[0037] Test 3: The photoresists prepared in Examples 1-3 and Comparative Examples 5-8 were spin-coated onto silicon wafers and baked to form a 5μm coating. The dielectric constant of the coating at 1MHz was measured using a broadband dielectric spectrometer. The test was repeated 3 times and the average value was taken. The results are shown in Table 3.

[0038] Table 3: Test results of photoresist dielectric constant Dielectric constant Example 1 2.38 Example 2 2.30 Example 3 2.25 Comparative Example 5 3.27 Comparative Example 6 2.92 Comparative Example 7 2.61 Comparative Example 8 2.86 As shown in Table 3, in Comparative Examples 5 and 7, the dielectric constant of the photoresist obtained by adding only nano-titanium dioxide hybrid particles or hollow silicon dioxide carbon spheres was higher than that of Example 1. In Comparative Example 6, the dielectric constant of the photoresist obtained by adding both nano-titanium dioxide hybrid particles and silicon dioxide core-shell particles (solid) was higher than that of Comparative Example 5, but lower than that of Comparative Example 7 and Example 1. In Comparative Example 8, the dielectric constant of the photoresist obtained by adding both hollow silicon dioxide spheres and nano-titanium dioxide was higher than that of Comparative Example 5, but still lower than that of Comparative Example 7. As can be seen from Example 7 and Example 1, by dissolving modified polyimide resin powder in a mixed solvent and then adding hollow carbon silica spheres and nano-titanium dioxide hybrid particles to form a photoresist, the hollow carbon silica spheres introduce a large amount of low dielectric constant air phase through their internal hollow cavity structure, directly constructing low dielectric micro-regions in a physical manner, becoming the core component for reducing the dielectric constant of the system. When used in conjunction with nano-titanium dioxide hybrid particles, they can synergistically reduce the dielectric constant of the photoresist and improve touch sensitivity and signal stability.

[0039] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A fabrication process for photoresist used in capacitive touch sensors, characterized in that, Includes the following steps: S1: Preparation of modified photosensitive agent 4-tert-butylphenol was nitrated under strong acid catalysis, and then the nitro group was reduced to an amino group by hydrogen catalysis using a Pd / C catalyst. Then it was reacted with ditert-butyl dicarbonate, then with iodobenzene and m-chloroperoxybenzoic acid, and finally with silver trifluoromethanesulfonate. After deprotection by trifluoroacetic acid, a modified photosensitive agent was obtained. S2: Preparation of modified polyimide resin powder S2.1: Add the diamine mixture containing the above modified photosensitive agent to N-methylpyrrolidone at a ratio of 1g:(8-10)mL, and simultaneously add 0.05-0.1% of hydroquinone polymerization inhibitor by total mass of the diamine mixture. Stir under nitrogen protection until completely dissolved, cool to 0-5℃, and add 4,4'-hexafluoroisopropylphthalic anhydride in 6-7 portions, with an interval of 10-15min each time. Then remove the ice-water bath and stir the reaction at room temperature for 6-8h to obtain polyamic acid prepolymer. S2.2: Triethylamine was added to the above polyamic acid prepolymer, followed by N-phenylmaleimide. The mixture was stirred at room temperature for 3-4 hours, and then azobisisobutyronitrile was added. The mixture was heated and stirred at 65-75°C for 1-2 hours under nitrogen protection. The mixture was then poured into 4 times its volume of a 50% ethanol aqueous solution to precipitate the precipitate. The precipitate was collected by filtration and then washed with deionized water and anhydrous ethanol in sequence. The mixture was subjected to gradient thermal imidization and vacuum drying to obtain modified polyimide resin powder. S3: Preparation of silica hollow carbon spheres and nano-titanium dioxide hybrid particles Nano-silica was dispersed in deionized water, and resorcinol and formaldehyde were added to react. Then, a hydrothermal reaction was carried out, followed by etching with dilute hydrofluoric acid solution to prepare hollow carbon spheres of silica. Subsequently, nano-titanium dioxide was dispersed in buffer solution, and dopamine hydrochloride was added to react to obtain nano-titanium dioxide hybrid particles. S4: Preparation of photoresist The modified polyimide resin powder was added to a mixed solvent and heated and stirred at 50-60°C until completely dissolved. Then, the silica hollow carbon spheres and nano-titanium dioxide hybrid particles were added. After ultrasonic dispersion for 30-40 minutes, the mixture was filtered through a 0.2μm polytetrafluoroethylene filter membrane and vacuum degassed for 20-30 minutes to obtain the photoresist.

2. The fabrication process of photoresist for a capacitive touch sensor according to claim 1, characterized in that, S1 includes the following steps: S1.1: Mix 4-tert-butylphenol, concentrated sulfuric acid, and glacial acetic acid in a ratio of (1.8-2.0) g: 1 mL: (7-9) mL and stir until completely dissolved. Cool to 0-2℃, add concentrated nitric acid (65 wt%) dropwise, stir for 1.5-2.5 h, pour into ice water and let stand to crystallize. Filter, wash with deionized water until neutral, and vacuum dry to obtain nitro-substituted 4-tert-butylphenol. The amount of concentrated nitric acid added is 3.5-4.5% of the volume of glacial acetic acid. S1.2: Add the above nitro-substituted 4-tert-butylphenol to anhydrous ethanol at a ratio of 1g:(10-12)mL, add a Pd / C catalyst with a palladium loading of 10wt%, introduce hydrogen to adjust the pressure to 0.1-0.2MPa, stir the reaction at 25-30℃ for 3-4h, filter to remove the catalyst, remove the solvent by rotary evaporation under reduced pressure to obtain amino-substituted 4-tert-butylphenol; S1.3: The above-mentioned amino-substituted 4-tert-butylphenol was added to anhydrous tetrahydrofuran at a ratio of 1g:(15-20)mL. After stirring and dissolving, di-tert-butyl dicarbonate and triethylamine were added. After stirring and reacting for 3-4 hours, the solvent was removed by rotary evaporation under reduced pressure, recrystallized and dried under vacuum to obtain Boc-amino-substituted 4-tert-butylphenol. The molar ratio of di-tert-butyl dicarbonate to amino-substituted 4-tert-butylphenol was (1.1-1.2):1, and the molar ratio of triethylamine to amino-substituted 4-tert-butylphenol was (1.2-1.3):

1. S1.4: In a molar ratio of 1:(1.05-1.1):(1.1-1.2), the above Boc-amino-substituted 4-tert-butylphenol, iodobenzene and m-chloroperoxybenzoic acid were added to dichloromethane and stirred at 25-30℃ for 5-6 h. The precipitate was removed by filtration, and silver trifluoromethanesulfonate was added to the filtrate. The mixture was stirred for 1-2 h, filtered, concentrated under reduced pressure, recrystallized and dried under vacuum to obtain the precursor. The ratio of Boc-amino-substituted 4-tert-butylphenol to dichloromethane was 1 g:(13-15) mL. S1.5: Dissolve the above precursor in dichloromethane at a ratio of 1g:(10-15)mL, add trifluoroacetic acid dropwise at 1-3℃, and after the addition is complete, return to room temperature and stir for 2-3h. Then remove the solvent and trifluoroacetic acid by rotary evaporation under reduced pressure, and then obtain the modified photocatalytic agent by recrystallization and vacuum drying. The volume ratio of trifluoroacetic acid to precursor is 1:

1.

3. The fabrication process of photoresist for a capacitive touch sensor according to claim 2, characterized in that, S3 includes the following steps: S3.1: Add nano-silica to deionized water at a ratio of 1g:(30-40)mL, disperse ultrasonically for 30-40min, then add resorcinol and formaldehyde, adjust the pH to 8.0-8.5 with 0.1mol / L sodium hydroxide solution, stir and react at 25-30℃ for 4-5h, then hydrothermally react at 175-185℃ for 5.5-6.5h, collect the product by centrifugation after cooling, wash, vacuum dry, and then calcine at 800-850℃ for 2-3h under a nitrogen atmosphere to obtain silica core-shell particles; S3.2: Add the above silica core-shell particles to anhydrous ethanol at a ratio of 1g:(20-30)mL, disperse ultrasonically for 30-40min, then add a 2wt% dilute hydrofluoric acid solution, stir and etch for 10-15min, then add an equal volume of anhydrous ethanol to terminate the reaction, and then centrifuge, wash and vacuum dry to obtain silica hollow carbon spheres. The amount of dilute hydrofluoric acid solution added is 20-30% of the volume of anhydrous ethanol. S3.3: Add nano-titanium dioxide to buffer solution at a ratio of 1g:(40-50)mL, disperse by ultrasonication in an ice bath at 1-3℃ for 40-50min, remove the ice bath, add dopamine hydrochloride, stir and react at room temperature in the dark for 10-12h, collect the precipitate by centrifugation, wash with deionized water and anhydrous ethanol 3-4 times respectively, and vacuum dry to obtain nano-titanium dioxide hybrid particles.

4. The fabrication process of photoresist for a capacitive touch sensor according to claim 2, characterized in that, The amount of Pd / C catalyst added is 2-3% of the mass of nitro-substituted 4-tert-butylphenol, and the molar ratio of silver trifluoromethanesulfonate to Boc-amino-substituted 4-tert-butylphenol is 1:(1-1.1).

5. The fabrication process of photoresist for a capacitive touch sensor according to claim 1, characterized in that, The molar ratio of the mixture of 4,4'-hexafluoroisopropylphthalic anhydride and diamine is 1:(0.99-1.01), and the diamine mixture is composed of a modified photosensitive agent, 2,2'-bis(trifluoromethylbenzidine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and 3-aminostyrene in a molar ratio of (0.05-0.08):(0.6-0.7):(0.2-0.25):(0.03-0.05).

6. The fabrication process of photoresist for a capacitive touch sensor according to claim 5, characterized in that, The amount of triethylamine is 1.1-1.2 times the molar amount of 3-aminostyrene, the amount of N-phenylmaleimide is 12-14% of the mass of 2,2'-bis(trifluoromethyl)benzidine, and the amount of azobisisobutyronitrile is 2.2-2.3% of the mass of N-phenylmaleimide.

7. The fabrication process of photoresist for a capacitive touch sensor according to claim 3, characterized in that, The molar ratio of resorcinol to formaldehyde is 1:1.5, and the mass ratio of resorcinol to nano-silica is (2.8-3.2):

1.

8. The fabrication process of photoresist for a capacitive touch sensor according to claim 3, characterized in that, The buffer solution was a Tris-HCl buffer solution with a concentration of 0.01 mol / L and a pH of 6.5-7, and the amount of dopamine hydrochloride added was 10% of the mass of nano-titanium dioxide.

9. The fabrication process of photoresist for a capacitive touch sensor according to claim 1, characterized in that, The photoresist is composed of the following raw materials by mass percentage: 25-30% modified polyimide resin powder, 1.5-2% hollow carbon silica spheres, 0.5-1% nano-titanium dioxide hybrid particles, and the balance being a mixed solvent, wherein the mixed solvent is composed of propylene glycol methyl ether acetate and γ-butyrolactone in a mass ratio of (4-5):

1.

10. A photoresist for a capacitive touch sensor, characterized in that, It is prepared by the photoresist preparation process for a capacitive touch sensor as described in any one of claims 1-9.

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