A colored photoresist composition of a high polarity solvent system and a method for preparing the same

Abstract

The application provides a colored photoresist composition of a high-polarity solvent system and a preparation method thereof, and relates to the technical field of photoresist materials. The colored photoresist composition comprises an alkali-soluble resin compound containing an unsaturated group, a photopolymerization monomer with an ethylenic unsaturated bond, a photopolymerization initiator, a surfactant, a carbon black dispersion liquid, an inorganic dye and a solvent. The solvent comprises ethyl lactate, and the content of the ethyl lactate is not less than 70 wt% based on the total weight of the solvent. The application uses ethyl lactate as a main solvent to improve process compatibility, combines the stable dispersion of the inorganic dye and the carbon black dispersion liquid, overcomes pigment agglomeration and realizes excellent light shielding, significantly improves the alkali resistance, adhesion and film surface quality of a dry film, and effectively prevents wire breakage.

Description

Technical Field

[0001] This invention relates to the field of photoresist materials technology, and more specifically, to a colored photoresist composition with a highly polar solvent system and its preparation method. Background Technology

[0002] Flexible displays are widely used in the display industry due to their foldable properties. In the manufacturing process of flexible screens, conductive arrays are typically arranged on a flexible transparent substrate (such as polyethylene terephthalate, polycarbonate, polyethylene naphthalate, etc.), and the required lines and patterns are formed through photolithography. The photoresist composition, as the core material for forming this type of dry film system, directly determines the alkali resistance of the final dry film and the overall performance of the product.

[0003] Existing photoresist systems often require a certain degree of light-shielding to mask the light reflection from the underlying conductive metal (such as copper wires) when forming wiring patterns. Therefore, pigments or dye dispersions (such as carbon black) are often introduced into the system for color adjustment. At the same time, conventional existing processes mostly rely on using common solvents such as propylene glycol methyl ether acetate as basic components for formulation.

[0004] However, traditional photolithography systems have significant limitations when facing more demanding processes. On the one hand, traditional solvents may adversely affect specific equipment or other chemicals used in subsequent processes. When attempting to replace them with large amounts of highly polar solvents to meet process requirements, the physicochemical environment of the system will change drastically. On the other hand, under such specific solvent conditions, traditional pigment dispersions such as carbon black exhibit poor compatibility, and the stability of the coloring system is easily compromised, resulting in severe particle agglomeration.

[0005] In summary, existing compositions struggle to balance process safety with stable internal pigment dispersion by adjusting the solvent system. Pigment agglomeration not only directly leads to a sharp deterioration in the film surface condition after deposition but also compromises the adhesion stability of the dry film in subsequent processes, resulting in a series of serious defects such as fine line breakage. This fails to meet the requirements of current processes for high sensitivity and reliability of the finished product.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a colored photoresist composition based on a highly polar solvent system and its preparation method. This application improves process compatibility and light-shielding performance through the stable dispersion and synergistic effect of the highly polar main solvent and the pigment system, effectively overcoming pigment agglomeration and improving the film quality and adhesion of the dry film.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides a colored photoresist composition in a highly polar solvent system, comprising an alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer having ethylene unsaturated bonds, a photopolymerization initiator, a surfactant, a carbon black dispersion, an inorganic dye, and a solvent. The solvent contains ethyl lactate, and the content of ethyl lactate is not less than 70 wt% based on the total weight of the solvent.

[0009] In an optional embodiment, the product comprises the following components by weight: 18 to 35 parts of alkali-soluble resin compounds containing unsaturated groups; 5 to 15 parts of photopolymerizable monomers with ethylene-unsaturated bonds; Photopolymerization initiator: 0.1 to 1 part; Surfactant: 0.1 to 0.5 parts; 2 to 5 parts carbon black dispersion; 5 to 15 parts of inorganic dye solution; Solvent: 40-65 parts.

[0010] In an optional embodiment, the solvent further comprises propylene glycol methyl ether acetate and / or propylene glycol monomethyl ether; Preferably, based on the total weight of the solvent, the content of propylene glycol methyl ether acetate is 0wt%~25wt%, the content of propylene glycol monomethyl ether is 0wt%~5wt%, and the sum of the contents of ethyl lactate, propylene glycol methyl ether acetate, and propylene glycol monomethyl ether is 100wt%.

[0011] In an optional embodiment, the inorganic dye includes a blue-violet dye; preferably, the inorganic dye is crystal violet; and / or, The photopolymerizable monomer is dipentaerythritol hexaacrylate.

[0012] In an optional embodiment, the carbon black dispersion satisfies at least one of the following conditions: A. The pH of the carbon black in the carbon black dispersion is 3.0~4.0; B. The average primary particle size of the carbon black in the carbon black dispersion is 20nm~30nm; C. The DBP oil absorption of carbon black in the carbon black dispersion is 90mL / 100g~110mL / 100g; D. The carbon black dispersion is obtained by dispersing a carbon black-containing dispersion system using a bead mill; preferably, the diameter of the zirconia beads used in the bead mill is 0.03 mm to 2.00 mm; more preferably, the dispersion process includes: pre-crushing with zirconia beads with a diameter of 0.8 mm to 1.2 mm, and then formally crushing with zirconia beads with a diameter of 0.05 mm to 0.2 mm.

[0013] In a second aspect, the present invention provides a photolithography substrate on which a pattern is formed on its surface by coating, exposing and developing a colored photoresist composition of a high polarity solvent system as described in any of the foregoing embodiments. Preferably, the substrate of the photolithography substrate is selected from at least one of glass, silicon wafer, polyethylene terephthalate, polycarbonate and polyethylene naphthalate.

[0014] Thirdly, the present invention provides a method for preparing a carbon black dispersion, used to prepare a carbon black dispersion in a colored photoresist composition of a high-polarity solvent system as described in any of the foregoing embodiments, the method comprising: Carbon black, dispersant, alkali-soluble resin and ethyl lactate are mixed and dispersed using a bead mill to obtain the carbon black dispersion. Preferably, the dispersion process includes: first, pre-crushing with zirconia beads with a diameter of 0.8 mm to 1.2 mm by vibration, and then formally crushing with zirconia beads with a diameter of 0.05 mm to 0.2 mm.

[0015] Fourthly, the present invention provides a method for preparing a colored photoresist composition of a highly polar solvent system as described in any of the foregoing embodiments, the method comprising: The photopolymerization initiator was added to the solvent and stirred until dissolved to obtain a mixture; An alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer with ethylene unsaturated bonds, a surfactant, an inorganic dye, and a carbon black dispersion are added sequentially to the mixture, and the mixture is stirred at room temperature to obtain the colored photoresist composition of the high polar solvent system.

[0016] Fifthly, the present invention provides a method for forming a fine line pattern on a flexible display screen, comprising: A colored photoresist composition of a high-polarity solvent system as described in any of the foregoing embodiments is coated onto a transparent substrate to form a coating film; The coated film is subjected to heat treatment; The heated coated film is exposed using a mask; The pattern is formed after developing with an alkaline developer and washing.

[0017] In an optional embodiment, the alkaline developing solution is an aqueous solution of potassium carbonate; Preferably, the concentration of the potassium carbonate aqueous solution is 0.5 wt% to 3.0 wt%. More preferably, the concentration of the potassium carbonate aqueous solution is 1 wt%.

[0018] Compared with the prior art, the composition provided in this application uses ethyl lactate as the main solvent. Its high polarity and hydroxyl-containing properties can be well adapted to the specific environment of flexible display manufacturing, effectively avoiding the adverse effects of traditional propylene glycol methyl ether acetate solvent on process equipment or subsequent process chemicals, thus improving process compatibility and overall safety.

[0019] Meanwhile, the carbon black dispersion and inorganic dyes in the system work synergistically to provide excellent light-blocking properties, effectively blocking reflected light from the copper wire conductive array on the flexible transparent substrate. This specific combination of components, in a highly polar solvent environment composed of a large amount of ethyl lactate, overcomes the defect of traditional pigments being prone to aggregation, maintains the high dispersion stability of the coloring system, and avoids film surface abnormalities caused by aggregation disrupting the stable state.

[0020] Furthermore, the aforementioned components, in combination with alkali-soluble resin compounds containing unsaturated groups, photopolymerizable monomers, photopolymerization initiators, and surfactants, result in a dry film with excellent alkali resistance after coating, and significantly improve photolithography, development performance, and adhesion to the substrate. This not only significantly improves the uniformity and quality of the film surface and effectively reduces process defects such as line breaks, but also further enhances the photosensitivity of the pattern and the overall reliability of the finished product. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a surface state diagram (OM observation diagram) of the coated film of Comparative Example 1 of this application. Figure 2 This is an OM observation diagram of the surface state of the coated film in Example 1 of this application. Figure 3 This is a schematic diagram of the pattern resolution of Comparative Example 1 of this application (OM observation diagram); Figure 4 This is a schematic diagram of the pattern resolution (OM observation diagram) of Embodiment 1 of this application; Figure 5This is a schematic diagram illustrating the copper plating masking effect on the metal wiring layer of the photolithographic substrate formed in the embodiments of this application. Figure 1 (OM observation diagram); Figure 6 This is a schematic diagram illustrating the copper plating masking effect on the metal wiring layer of the photolithographic substrate formed in the embodiments of this application. Figure 2 (OM observation diagram); Figure 7 This illustration shows the poor copper shielding effect of the photolithographic substrate formed in the comparative example of this application on the metal wiring layer. Figure 1 (OM observation diagram); Figure 8 This illustration shows the poor copper shielding effect of the photolithographic substrate formed in the comparative example of this application on the metal wiring layer. Figure 2 (OM observation diagram). Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0024] This embodiment provides a colored photoresist composition with a high polarity solvent system, which is mainly used in fields such as flexible display manufacturing where the safety of solvents and the light-shielding properties of coatings are strictly required.

[0025] The colored photoresist composition includes an alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer having ethylene unsaturated bonds, a photopolymerization initiator, a surfactant, a carbon black dispersion, an inorganic dye, and a solvent.

[0026] In this composition, the choice of solvent plays a crucial role in ensuring the stability of the process equipment and the compatibility of subsequent chemicals. The solvent comprises ethyl lactate, and the content of ethyl lactate is not less than 70 wt% by weight of the total solvent. Based on the percentage attribute, a reasonable implicit upper limit is 100 wt%. For example, it can be 70 wt%, 75 wt%, 78 wt%, 80 wt%, 85 wt%, 88 wt%, 92 wt%, 95 wt%, 98 wt%, 100 wt%, etc. Using this high proportion of ethyl lactate to construct a highly polar solvent system effectively avoids the adverse effects of conventional solvents on the process environment.

[0027] In this highly polar solvent system, inorganic dyes and carbon black dispersions work synergistically to form a stable coloring and opacifying system. The inorganic dyes provide targeted complementary colors, while the carbon black dispersions further enhance the hiding power. Both exhibit excellent dispersion stability in a solvent system primarily composed of ethyl lactate, preventing agglomeration.

[0028] During film formation, alkali-soluble resin compounds containing unsaturated groups provide the basic framework and alkali development capability. Under exposure conditions, photopolymerization initiators excite free radicals, promoting rapid cross-linking reactions of photopolymerizable monomers with vinyl unsaturated bonds, forming a dense cured network. Combined with the leveling effect of surfactants, this composition can form fine line patterns with uniform thickness, good adhesion to the substrate, and excellent alkali resistance on flexible transparent substrates, exhibiting excellent anti-breakage and light-shielding properties.

[0029] In summary, the composition provided in this application uses ethyl lactate as the main solvent, improving the compatibility of the processing equipment and subsequent processes. Simultaneously, the carbon black dispersion and inorganic dyes maintain excellent dispersion stability in a specific highly polar environment, overcoming the tendency of traditional pigments to agglomerate, and providing good light-blocking properties to mask the reflection of copper wires. The synergistic effect of the components results in a dry film with excellent alkali resistance, photosensitivity, and adhesion to the substrate, significantly improving film quality and effectively reducing defects such as broken lines, thereby obtaining highly reliable fine line patterns.

[0030] To balance the photolithographic performance, light-shielding properties, and film quality of the colored photoresist composition, the weight ratio of each component in the composition was adjusted in this embodiment. In some embodiments, the composition includes the following components by weight: (1) 18 to 35 parts of alkali-soluble resin compound containing unsaturated groups; for example, it can be 18 parts, 20 parts, 22 parts, 25 parts, 26.4 parts, 28 parts, 30 parts, 32.5 parts, 34 parts, 35 parts, etc.

[0031] (2) 5 to 15 parts of photopolymerizable monomers with ethylene unsaturated bonds; for example, it can be 5 parts, 6 parts, 7 parts, 8.27 parts, 9 parts, 10 parts, 11 parts, 12 parts, 14 parts, 15 parts, etc.

[0032] (3) Photopolymerization initiator 0.1 to 1 part; for example, it can be 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part, 1 part, etc.

[0033] (4) 0.1 to 0.5 parts of surfactant; for example, it can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.

[0034] (5) 2 to 5 parts of carbon black dispersion; for example, it can be 2 parts, 2.3 parts, 2.6 parts, 3 parts, 3.5 parts, 3.75 parts, 4 parts, 4.2 parts, 4.6 parts, 5 parts, etc.

[0035] (6) 5 to 15 parts of inorganic dye solution; for example, it can be 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, etc.

[0036] (7) Solvent 40 to 65 parts. For example, it can be 40 parts, 44.88 parts, 48 ​​parts, 50.98 parts, 55 parts, 58.63 parts, 60 parts, 62 parts, 64 parts, 65 parts, etc.

[0037] In the above formulation system, the alkali-soluble resin compound containing unsaturated groups and the photopolymerizable monomer with vinyl unsaturated bonds jointly determine the film-forming properties and alkali resistance of the composition. By limiting the resin compound to 18-35 parts and the photopolymerizable monomer to 5-15 parts, a moderate difference in dissolution rate can be maintained in the alkaline developer, ensuring that the unexposed areas can be completely dissolved without leaving residue, while also ensuring sufficient cross-linking in the exposed areas, resulting in excellent pattern adhesion.

[0038] The dosage of photopolymerization initiator (0.1 to 1 part) and surfactant (0.1 to 0.5 parts) are matched to ensure photosensitivity while enabling the photoresist composition to have good leveling properties during coating, avoiding flow marks or pinhole defects.

[0039] Furthermore, a highly stable dispersed phase was formed by carbon black dispersion (2-5 parts) and inorganic dye solution (5-15 parts) in a solvent medium of 40-65 parts. Due to the significant proportion of highly polar components such as ethyl lactate in the solvent system, the aforementioned specific proportion of coloring components exhibits microscopic affinity with the resin compound, thereby preventing the aggregation and coarsening of carbon black particles in a highly polar environment. After film formation, the coloring system within this proportion range can efficiently absorb and reduce reflected light from the copper wire array beneath the transparent substrate, significantly reducing film quality deterioration and fine line breakage caused by pigment agglomeration, ultimately achieving highly reliable colored patterns.

[0040] In some preferred embodiments, in order to further optimize the coating leveling properties of the colored photoresist composition and adjust its evaporation and drying rate, the solvent, in addition to the main solvent ethyl lactate, optionally includes a mixed solvent system consisting of propylene glycol methyl ether acetate and / or propylene glycol monomethyl ether.

[0041] Furthermore, based on the total weight of the solvent, the content of propylene glycol methyl ether acetate is 0wt%~25wt%, and the content of propylene glycol monomethyl ether is 0wt%~5wt%. By strictly controlling the content of the traditional propylene glycol methyl ether acetate solvent to 25wt% or less, it can be ensured that the use of this composition will not have an adverse effect on subsequent processing equipment and other chemical substances used in the process.

[0042] Meanwhile, trace amounts of propylene glycol monomethyl ether can be used to fine-tune the solvent evaporation gradient of the coating during the heat treatment stage. Furthermore, the total content of the ethyl lactate, propylene glycol methyl ether acetate, and propylene glycol monomethyl ether is limited to 100 wt%, thereby creating a stable and closed solvent environment. This solvent combination, with its specific ratio, can maintain the high polarity of the system while promoting the uniform dissolution and stable dispersion of each solid component, effectively preventing line breaks or uneven film formation, and ensuring excellent film quality of the photoresist on the transparent substrate.

[0043] In some more preferred embodiments, the coloring system, monomer type, and dispersion process in the composition were further optimized to maximize the light-blocking effect of the composition and improve the dispersion stability in highly polar environments.

[0044] Regarding the coloring system, since the copper conductive array under the flexible screen reflects light and affects the visual experience, and blue is the best complementary color to the color of copper metal, in an optional embodiment, the inorganic dye includes a blue-violet dye; further, the inorganic dye is crystal violet.

[0045] Crystal violet not only provides excellent complementary shading effects but also exhibits excellent solubility in highly polar solvents, primarily ethyl lactate. Combined with a small amount of carbon black dispersion in the system, it achieves good shading with extremely low addition amounts, effectively reducing system instability caused by adding large quantities of a single pigment. It should be noted that the molecular formula of crystal violet (also known as CI Basic Violet 3 or CI 42555, CAS No. 548-62-9) is C1. 25 H 30 ClN3 has a molecular weight of 408. This dye exhibits excellent solubility in ethyl lactate (EL) solvent, but extremely low solubility in conventional propylene glycol methyl ether acetate (PMA) solvent.

[0046] In terms of photopolymerization network construction, in some alternative embodiments, the photopolymerizable monomer is dipentaerythritol hexaacrylate. This multifunctional monomer can rapidly provide a high crosslinking density in the exposure zone, giving the coated film excellent alkali resistance and superior substrate adhesion.

[0047] To address the issue of carbon black's tendency to agglomerate in highly polar solvents, this solution not only regulates chemical compatibility but also limits the carbon black raw materials and physical dispersion methods. In some embodiments, the carbon black dispersion meets at least one of the following conditions: A. The pH of the carbon black in the carbon black dispersion is 3.0~4.0; for example, it can be 3.0, 3.2, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, etc. Within this range, the surface interaction between carbon black and dispersant can be kept at an optimal balance.

[0048] B. The average primary particle size of the carbon black in the carbon black dispersion is 20nm~30nm; for example, it can be 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 30nm, etc., to take into account both the requirements of light blocking rate and high resolution fine line pattern.

[0049] C. The DBP oil absorption of the carbon black in the carbon black dispersion is 90mL / 100g~110mL / 100g; for example, it can be 90mL / 100g, 93mL / 100g, 96mL / 100g, 99mL / 100g, 100mL / 100g, 102mL / 100g, 104mL / 100g, 106mL / 100g, 108mL / 100g, 110mL / 100g, etc.

[0050] D. The carbon black dispersion is obtained by dispersing a carbon black-containing dispersion system using a bead mill; further, the bead mill uses zirconia beads with a diameter of 0.03mm to 2.00mm (e.g., 0.03mm, 0.05mm, 0.1mm, 0.3mm, 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 2.00mm, etc.); even further, the dispersion process includes: first using beads with a diameter of 0.8mm to 1.2mm (e.g., 0.8mm, 0.85mm, 0.85mm, etc.). Zirconia beads with diameters of 9mm, 0.95mm, 1.0mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, etc. are pre-crushed, and then zirconia beads with diameters of 0.05mm to 0.2mm (e.g., 0.05mm, 0.07mm, 0.09mm, 0.1mm, 0.12mm, 0.14mm, 0.16mm, 0.18mm, 0.2mm, etc.) are used for formal crushing. This step-by-step grinding strategy can effectively avoid secondary agglomeration of carbon black particles and significantly improve the surface smoothness of the obtained photoresist film layer.

[0051] In the process of preparing dispersions, the dispersers used for dispersion treatment are not limited to bead mills, but can also be double-roll or triple-roll mills, ball mills, vibratory ball mills, paint mixers, continuous disc bead mills or continuous ring bead mills, etc.

[0052] This embodiment provides a photolithography substrate, which is mainly used in electronic devices that require high-precision light-shielding wiring, such as flexible displays or touch screens.

[0053] The photolithographic substrate has a predetermined fine line pattern formed on its surface. This pattern is formed by curing a series of photolithography processes, such as coating, exposure, and development, with a colored photoresist composition based on the aforementioned high-polarity solvent system.

[0054] Specifically, the underlying support structure of the photolithography substrate is a substrate. To adapt to different application scenarios, especially the needs of flexible foldable displays, the substrate is selected from at least one of glass, silicon wafer, polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN).

[0055] The pattern formation process specifically includes: First, uniformly coating the prepared colored photoresist composition (e.g., after filtration through a 1μm aperture) onto the transparent substrate at a specific film thickness (e.g., 1μm) to form a coating film; then allowing it to stand and undergo heat treatment (e.g., treatment with a 90°C heating plate for 1 minute) to allow the highly polar solvent in the system to evaporate smoothly, resulting in a dry film with a smooth surface; next, using a mask with a specific resolution test pattern, subjecting the coated substrate to ultraviolet exposure (e.g., 40mJ / cm²). 2 The exposure amount is increased to allow the resin and monomer in the exposed area to undergo deep cross-linking polymerization, which encapsulates and fixes the inorganic dye and carbon black particles in a stable dispersed state, and generates strong adhesion to the substrate. Finally, an alkaline developer (such as a 1 wt% potassium carbonate aqueous solution) is used for development treatment and washed with pure water to dissolve and remove the unexposed areas, and finally solidifies on the substrate to form a fine pattern with high light-blocking rate and high resolution.

[0056] By combining the above materials with a specific substrate, the resulting photolithography substrate not only has clear pattern lines and no granular roughness defects on the surface, but also exhibits excellent alkali resistance and adhesion to the flexible substrate. It can effectively block light reflection from the conductive material below the substrate, meeting the manufacturing requirements of high-sensitivity display devices.

[0057] In preparing the colored photoresist composition using the aforementioned high-polarity solvent system, carbon black dispersion, as the core coloring intermediate, directly determines the optical properties and physical yield of the final dry film due to its dispersion stability. This application also provides a method for preparing a carbon black dispersion for use in the aforementioned high-polarity solvent system colored photoresist composition. This method, through a combination of a specific formulation system and a multi-stage grinding process, effectively overcomes the technical challenge of easy agglomeration of pigment particles in hydroxyl-containing high-polarity solvents. The method includes: Carbon black, dispersant, alkali-soluble resin and ethyl lactate are mixed and dispersed using a bead mill to obtain the carbon black dispersion.

[0058] In this system, ethyl lactate provides a highly polar liquid environment suitable for subsequent photolithography processes; the high-energy shear force provided by the dispersant breaks up the initial aggregated state of the carbon black; and the dispersant and alkali-soluble resin synergistically coat the surface of the pulverized fine carbon black particles, constructing a microscopic defense through steric hindrance to prevent secondary agglomeration of the particles in the ethyl lactate medium. In actual production, the raw materials can first be thoroughly wetted using a known mixer, and then pumped into a bead mill for circulating dispersion.

[0059] Furthermore, in order to achieve a highly uniform micro-dispersion effect at the nanoscale and improve grinding efficiency, the bead diameter of the zirconia beads used in the bead mill is preferably 0.03 mm to 2.00 mm. For example, it can be 0.03 mm, 0.05 mm, 0.1 mm, 0.3 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm, 2.00 mm, etc. The dispersion process includes: first, pre-crushing with zirconia beads with a diameter of 0.8mm to 1.2mm (e.g., 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, etc.) using vibration, rapidly disintegrating large hard agglomerates of carbon black using the high impact kinetic energy of the larger grinding media; then, formal crushing with zirconia beads with a diameter of 0.05mm to 0.2mm (e.g., 0.05mm, 0.07mm, 0.09mm, 0.1mm, 0.12mm, 0.14mm, 0.16mm, 0.18mm, 0.2mm, etc.). The particles are further finely ground using the high-frequency micro-shear force generated by the small beads. The smooth transition between these two processes not only avoids damage to the molecular structure of the dispersant caused by excessive grinding, but also significantly narrows the particle size distribution of carbon black. This results in the final dispersion exhibiting excellent dispersion stability and resistance to coarsening when subsequently formulating photoresist compositions, laying a solid material foundation for the formation of high-resolution fine line patterns.

[0060] This application also provides a method for preparing a colored photoresist composition in a high-polarity solvent system. This method, through a scientifically designed feeding sequence and mild mixing conditions, ensures high uniformity and stability of the photosensitive and coloring components in a specific high-polarity solvent system. The preparation method specifically includes the following steps: S1, add the photopolymerization initiator to the solvent and stir until dissolved to obtain a mixture.

[0061] Specifically, the prescribed amount of photopolymerization initiator can be added to the solvent, and the stirring device can be turned on to keep stirring until the solid components are completely dissolved, resulting in a uniform and transparent initiator mixture. In the initial stage of preparation, the low viscosity and high solubility of the pure solvent are preferentially used to achieve molecular-level dispersion of the photopolymerization initiator, which helps to reduce local exposure micro-defects caused by insufficient dissolution of solid powder in the subsequent high viscosity system.

[0062] S2, add in sequence an alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer with ethylene unsaturated bonds, a surfactant, an inorganic dye, and a carbon black dispersion to the mixture, and stir at room temperature to obtain the colored photoresist composition of the high polarity solvent system.

[0063] In this step, an alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer with ethylene unsaturated bonds, a surfactant, an inorganic dye, and a pre-prepared carbon black dispersion are sequentially and quantitatively added to the initiator mixture obtained above, while continuous stirring at room temperature. This order of addition allows the basic film-forming resin and monomer to expand in the solvent first, and the subsequently added carbon black dispersion can be uniformly mixed into the system under the steric hindrance protection of the resin molecular chains, effectively avoiding the instantaneous aggregation and coarsening of the coloring pigments in a highly polar environment.

[0064] During the above stirring process, the ambient temperature is controlled at room temperature (typically for 1 hour of stirring) to avoid high temperatures causing initial thermal polymerization of the photopolymerizable monomers or initiator failure, thereby ensuring the chemical stability and shelf life of the composition. After uniform mixing, the colored photoresist composition of the high-polarity solvent system is obtained.

[0065] In some preferred implementation scenarios, in order to meet the stringent requirements of high-precision flexible display manufacturing processes for particulate matter, after the composition is obtained by stirring at room temperature, a micron-sized (e.g., 1 μm) filter device can be used to perform precision filtration on the composition to further remove impurities or micro-aggregates in the system, ensuring the surface smoothness and high resolution of the coated film.

[0066] This application provides a method for forming fine line patterns on a flexible display screen. The method utilizes the aforementioned colored photoresist composition with a high polarity solvent system to prepare patterns with high light-shielding properties, high resolution, and excellent adhesion on a transparent substrate.

[0067] S10, the method for forming the fine line pattern of the flexible display screen specifically includes the following steps: coating a colored photoresist composition of a high polarity solvent system as described above onto a transparent substrate to form a coating film.

[0068] Specifically, the prepared colored photoresist composition of the high-polarity solvent system is coated onto a transparent substrate to form a coating film. In practice, to obtain a uniform film thickness, a spin coating device can be used for coating, and the final film thickness can be controlled at a specific size by adjusting the spin coating parameters (e.g., coating onto a transparent substrate such as glass or PET with a film thickness of 1 μm).

[0069] S20, the coated film is subjected to heat treatment.

[0070] This step aims to allow the highly polar solvent within the coated film to evaporate smoothly, transforming the liquid composition into a non-sticky solid dry film. The heating process can be performed using equipment such as a heating plate (e.g., after a short period of stillness, heat the coated substrate at 90°C for approximately 1 minute using a heating plate). Appropriate heating conditions ensure complete solvent evaporation without causing bubbles or surface crusting within the coating, thus maintaining the high dispersion stability of the coloring system.

[0071] S30, using a mask to expose the heated coated film.

[0072] In this step, light shines through the transparent area of ​​the mask onto the coated film (e.g., using a resolution testing mask at 40 mJ / cm²). 2 The coating film is exposed to ultraviolet light (the exposure amount is increased). The photopolymerization initiator in the exposed area generates free radicals, which initiate the rapid cross-linking polymerization of monomers and alkali-soluble resins, forming a three-dimensional network with high mechanical strength and alkali resistance, and firmly encapsulating carbon black and dyes within it.

[0073] S40 uses an alkaline developer for development, and the pattern is formed after washing.

[0074] In areas not exposed to light, where no cross-linking polymerization has occurred, the alkali-soluble resin components are dissolved and removed by an alkaline developer (e.g., an alkaline developer containing 1% potassium carbonate aqueous solution). The developing reaction is then terminated and residues are rinsed away with pure water. Thanks to the superior anti-agglomeration properties and strong adhesion of the aforementioned composition, the resulting fine line pattern is free of breaks and developing residues, and effectively blocks reflected light from the bottom of the substrate, meeting the high-standard manufacturing requirements of flexible displays.

[0075] In the process of forming fine line patterns on flexible displays, the chemical environment control of the developing step has a decisive impact on the final resolution and morphological integrity of the pattern. In order to achieve precise developing results and protect the solidified fine pattern, this embodiment has specifically selected and optimized the concentration of the alkaline developing solution used in the developing step.

[0076] In some optional embodiments, the alkaline developer is an aqueous solution of potassium carbonate. Using potassium carbonate, a weakly alkaline salt, as the developing medium allows for the dissociation of appropriate amounts of hydroxide ions in the aqueous solution. These ions react with the unsaturated, alkali-soluble resin in the unexposed areas through an acid-base neutralization reaction, converting the resin to a water-soluble state and allowing it to be washed away. This mild alkaline system not only prevents chemical corrosion of the flexible transparent substrate material during the developing process but also effectively prevents excessive lateral dissolution of the exposed, cross-linked, and cured areas by the developer, thus ensuring the physical integrity of the fine line pattern.

[0077] To achieve the optimal balance between thorough development and pattern retention, the concentration of the potassium carbonate aqueous solution is further 0.5 wt% to 3.0 wt%; for example, it can be 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, 2.5 wt%, 2.8 wt%, 3.0 wt%, etc. Even more specifically, the concentration of the potassium carbonate aqueous solution is 1 wt%.

[0078] If the developer concentration is too low, the neutralization reaction rate is slow, and undissolved resin and coloring particles are easily left on the substrate surface or in the gaps between fine lines, forming development residue. If the concentration is too high, the developer is too aggressive, which will lead to increased swelling of the cross-linked network, resulting in edge peeling or breakage of the fine line pattern. More preferably, in this embodiment, a 1 wt% potassium carbonate aqueous solution is used for development. At this specific concentration, the development rate and the alkali resistance of the pattern are well matched. The unexposed areas dissolve quickly and completely, while the exposed areas have sharp edges and strong adhesion. Finally, a residue-free, highly reliable colored fine wiring pattern is obtained on the flexible display substrate.

[0079] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0080] I. Experimental Materials and Instructions: The raw materials used in the embodiments and comparative examples of this application are all commercially available. The main raw material information is as follows: Carbon black: MA100, pH 3.5, average primary particle size 24nm, DBP oil absorption 100mL / 100g (manufactured by Mitsubishi Chemical Corporation).

[0081] Dispersants: DISPERBYK-167 (52% solids, manufactured by BYK Chemical Company), DISPERBYK-21116 (40% solids, manufactured by BYK Chemical Company).

[0082] Alkali-soluble resins: V-259ME (solid content 56.2%, manufactured by Nippon Steel Chemical Materials), SP-DW-1009 (solid content 32.4%, manufactured by RESONAC), SP-DW-1011 (solid content 40%, manufactured by RESONAC).

[0083] Solvents: EL (ethyl lactate), PGMEA (propylene glycol methyl ether acetate, i.e., PMA), PGME (propylene glycol monomethyl ether, i.e., PM).

[0084] Photopolymerization initiators: IrgacureOXE02, IrgacureOXE03 (manufactured by BASF).

[0085] Photopolymer monomer: DPHA (dipentaerythritol hexaacrylate, manufactured by Nippon Pharmaceutical Co., Ltd.)

[0086] Surfactant: NSAD002 (manufactured by Nippon Steel Chemical Materials Co., Ltd.)

[0087] Inorganic dyes: Crystal Violet, a blue-violet dye, has excellent solubility in EL solvents, but extremely low solubility in PMA solvents.

[0088] II. Example of carbon black dispersion preparation: Preparation Example 1 This preparation example provides a method for preparing carbon black dispersion e1, which aims to investigate the dispersion effect of using a specific dispersant in combination with a resin in a highly polar ethyl lactate system.

[0089] Preparation method: In a 500ml bottle, 142.5 parts by weight of ethyl lactate (EL), 75 parts by weight of carbon black MA100, 45 parts by weight of DISPERBYK-21116 (40%), and 37.5 parts by weight of SP-DW-1011 (40%) were added sequentially. 150 parts by weight of zirconia beads with a particle size of 1.0mm were added, and the mixture was shaken for 2 hours using a paint mixer (manufactured by Asada Iron Works) as pre-crushing. Then, 200 parts by weight of zirconia beads with a particle size of 0.1mm were added, and the mixture was dispersed using a paint mixer for 8 hours as formal crushing, yielding carbon black dispersion e1.

[0090] Preparation Examples 2-4 Preparation Examples 2-4 provide methods for preparing carbon black dispersions e2, e3, and e4, respectively, and investigate the adaptability of different dispersants and resins to the preparation process.

[0091] Preparation method: Except for adjusting the mass fractions of each component according to the following formula table, the other operation steps are exactly the same as those in Preparation Example 1.

[0092] The raw material formulations for each preparation example are shown in the table below: Table 1. Carbon Black Dispersion Formulation Table

[0093] III. Preparation of Colored Photoresist Compositions and Photolithographic Substrates in Highly Polar Solvent Systems (Examples and Comparative Examples) Example 1 This embodiment provides a colored photoresist composition a1 with a high polarity solvent system and a method for forming a photolithographic substrate using the same. The main focus is on the performance of this specific formulation in the coating, exposure and development processes.

[0094] Preparation method: (1) Glue preparation: Add 0.1g of photoinitiator IrgacureOXE02 and 0.3g of Irgacure OXE03 to 58.63g of ethyl lactate (EL) and stir until the solid components are dissolved; then add alkali-soluble resin V-259ME (18.75g), photopolymerizable monomer dipentaerythritol hexaacrylate (8.27g), surfactant NSAD002 solution (0.2g), inorganic dye crystal violet solution (10g) and the carbon black dispersion e1 (3.75g) prepared above, and stir at room temperature for 1 hour to obtain a photosensitive black resin composition a1 with a total solid component concentration of 20%.

[0095] (2) Film formation: The composition a1 prepared by filtration with a 1 μm aperture was coated onto a transparent substrate such as glass or PET with a film thickness of 1 μm using a spin coater. After standing for 2 minutes, it was heated for 1 minute with a heating plate at 90°C. The coated film was exposed to ultraviolet light with an exposure dose of 40 mJ / cm2 using a resolution test mask. Then, it was developed with an alkaline developer solution of 1 wt% potassium carbonate aqueous solution, washed with pure water, and a pattern was formed to obtain a photolithographic substrate.

[0096] Examples 2-13 and Comparative Examples 1-3 This section provides colored photoresist compositions with various formulation ratios (a2-a13) and comparative formulations (a14-a16) to investigate the effects of different component ratios and the use of commercially available conventional carbon black dispersions on the final performance.

[0097] Preparation method: Weigh each component according to the following formula table, and mix (A) alkali-soluble resin, (B) photopolymerizable monomer, (C) photoinitiator, (D) surfactant (leveling agent), (E) carbon black dispersion, (F) inorganic dye and (G) solvent. The subsequent film formation and exposure and development process is the same as in Example 1.

[0098] The formulations of each embodiment and comparative example are shown in the table below (unit: g): Table 2. Proportions of the Examples and Comparative Examples

[0099] Note: e5 in the comparative example is the commercially available conventional carbon black dispersion NSCB001.

[0100] IV. Experimental Example: Film Formation and Dispersion Performance Test and Analysis: This experimental example aims to observe and evaluate the performance of the photoresist compositions and dry film patterns obtained in the above examples and comparative examples using optical microscopy (OM), mainly examining the surface particle aggregation and dispersion effect.

[0101] 1. Evaluation Results: The performance evaluation results of each sample are shown in the table below: Table 3. Performance Evaluation Results

[0102] In the performance evaluation table of the above experimental examples, the specific definitions of each symbol are as follows: "A": Indicates excellent performance. Specifically, the corresponding carbon black dispersion exhibits excellent dispersion stability in the photoresist composition, resulting in a smooth film surface with no visible particles under OM (Optical Markov Model), high pattern resolution, and no broken lines, meeting the requirements of high-performance flexible displays.

[0103] "B": Indicates good performance. The corresponding carbon black dispersion exhibits good dispersion stability, excellent film quality, and can meet the needs of daily processes.

[0104] "C": Indicates average performance. This corresponds to a slight risk of agglomeration in the carbon black dispersion, and the occasional appearance of a small number of fine particles in the film, which may have some impact on the formation of high-precision circuits.

[0105] "D": Indicates poor performance. This corresponds to severe agglomeration of the carbon black dispersion, resulting in a rough film surface after formation. Significant defects such as broken lines and residues appear after development, failing to meet the process requirements for high-reliability circuit wiring.

[0106] 2. Results and Figure Analysis: For comparative examples 1 to 3, combined with Figure 1 (Poor dispersion effect under OM observation) Figure 3 (Illustration of poor resolution under OM observation) and Figure 7 , Figure 8 (Schematic diagram of poor copper plating masking effect) It can be seen that when using commercially available conventional carbon black dispersion (e5), the stable state of the coloring system is severely disrupted, whether in the dominant high-polarity ethyl lactate or in a mixed solvent system (as shown in Table 3, the comparative dispersion effect is rated "D"). After film formation, surface particles are severe, and the fine line resolution of the dry film after exposure and development is extremely low. Especially when masking reflective metal lines (such as copper lines) on transparent flexible substrates, the pattern edges are rough, residue is obvious, and the masking effect is poor, failing to meet the requirements for high-reliability light-shielding wiring.

[0107] For Examples 1 to 13, in combination Figure 2 (A better dispersion effect diagram under OM observation) Figure 4 (A diagram showing better resolution under OM observation) and Figure 5 , Figure 6 (Schematic diagram of excellent copper plating shielding effect) It can be seen that the carbon black dispersion (e1-e4) prepared by this application using a specific bead milling process exhibits excellent dispersion stability in high polarity environments with different ratios (including pure EL system and mixed solvent system).

[0108] As shown in Table 3, the surface particle size and dispersion effects of all embodiments reached an excellent level of "A" or "B". After the photolithography process, not only are the edges of the final fine line pattern extremely sharp (corresponding to...) Figure 4 Furthermore, in applications targeting highly reflective metallic substrates (such as copper wires), the illustrated pattern enables precise coverage and efficient masking, with no burrs or risk of breakage at the edges (corresponding to...). Figure 5 and Figure 6 This significantly improves the problem of film quality deterioration caused by highly polar solvents.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A colored photoresist composition in a highly polar solvent system, characterized in that, Including alkali-soluble resin compounds containing unsaturated groups, photopolymerizable monomers with ethylene unsaturated bonds, photopolymerization initiators, surfactants, carbon black dispersions, inorganic dyes, and solvents; The solvent contains ethyl lactate, and the content of ethyl lactate is not less than 70 wt% based on the total weight of the solvent.

2. The colored photoresist composition of the high polarity solvent system as described in claim 1, characterized in that, By weight, it includes the following components: 18 to 35 parts of alkali-soluble resin compounds containing unsaturated groups; 5 to 15 parts of photopolymerizable monomers with ethylene-unsaturated bonds; Photopolymerization initiator: 0.1 to 1 part; Surfactant: 0.1 to 0.5 parts; 2 to 5 parts carbon black dispersion; 5 to 15 parts of inorganic dye solution; Solvent: 40-65 parts.

3. The colored photoresist composition of the high polarity solvent system as described in claim 1, characterized in that, The solvent further comprises propylene glycol methyl ether acetate and / or propylene glycol monomethyl ether; Preferably, based on the total weight of the solvent, the content of propylene glycol methyl ether acetate is 0wt%~25wt%, the content of propylene glycol monomethyl ether is 0wt%~5wt%, and the sum of the contents of ethyl lactate, propylene glycol methyl ether acetate, and propylene glycol monomethyl ether is 100wt%.

4. The colored photoresist composition of the high polarity solvent system as described in claim 1, characterized in that, The inorganic dye includes a blue-violet dye; preferably, the inorganic dye is crystal violet; and / or, The photopolymerizable monomer is dipentaerythritol hexaacrylate.

5. The colored photoresist composition of the high polarity solvent system as described in claim 1, characterized in that, The carbon black dispersion meets at least one of the following conditions: A. The pH of the carbon black in the carbon black dispersion is 3.0~4.0; B. The average primary particle size of the carbon black in the carbon black dispersion is 20nm~30nm; C. The DBP oil absorption of carbon black in the carbon black dispersion is 90mL / 100g~110mL / 100g; D. The carbon black dispersion is obtained by dispersing a carbon black-containing dispersion system using a bead mill; preferably, the diameter of the zirconia beads used in the bead mill is 0.03 mm to 2.00 mm; more preferably, the dispersion process includes: pre-crushing with zirconia beads with a diameter of 0.8 mm to 1.2 mm, and then formally crushing with zirconia beads with a diameter of 0.05 mm to 0.2 mm.

6. A photolithography substrate, characterized in that, Its surface is formed with a pattern formed by coating, exposing and developing a colored photoresist composition of a high polarity solvent system as described in any one of claims 1-5; Preferably, the substrate of the photolithography substrate is selected from at least one of glass, silicon wafer, polyethylene terephthalate, polycarbonate and polyethylene naphthalate.

7. A method for preparing a carbon black dispersion, characterized in that, The method for preparing a carbon black dispersion in a colored photoresist composition of a high-polarity solvent system as described in any one of claims 1-5, the method comprising: Carbon black, dispersant, alkali-soluble resin and ethyl lactate are mixed and dispersed using a bead mill to obtain the carbon black dispersion. Preferably, the dispersion process includes: first, pre-crushing with zirconia beads with a diameter of 0.8 mm to 1.2 mm by vibration, and then formally crushing with zirconia beads with a diameter of 0.05 mm to 0.2 mm.

8. A method for preparing a colored photoresist composition in a highly polar solvent system as described in any one of claims 1-5, characterized in that, The method includes: The photopolymerization initiator was added to the solvent and stirred until dissolved to obtain a mixture; An alkali-soluble resin compound containing unsaturated groups, a photopolymerizable monomer with ethylene unsaturated bonds, a surfactant, an inorganic dye, and a carbon black dispersion are added sequentially to the mixture, and the mixture is stirred at room temperature to obtain the colored photoresist composition of the high polar solvent system.

9. A method for forming a fine line pattern on a flexible display screen, characterized in that, include: A colored photoresist composition of a high-polarity solvent system as described in any one of claims 1-5 is coated onto a transparent substrate to form a coating film; The coated film is subjected to heat treatment; The heated coated film is exposed using a mask; The pattern is formed after developing with an alkaline developer and washing.

10. The method for forming a fine line pattern on a flexible display screen as described in claim 9, characterized in that, The alkaline developing solution is an aqueous solution of potassium carbonate. Preferably, the concentration of the potassium carbonate aqueous solution is 0.5 wt% to 3.0 wt%. More preferably, the concentration of the potassium carbonate aqueous solution is 1 wt%.

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