Super black gel pen ink composition and gel pen refill

Abstract

The invention discloses a super black gel pen ink composition and a gel pen refill, the ink composition comprises 15%-25% of a composite black nano pigment, 1%-3% of a light absorption enhancer, 5%-10% of a dispersant, 50%-80% of an aqueous solvent, 1%-3% of a hydrophobic cross-linking agent, 0.3%-1.5% of a pH regulator, 0.1%-0.3% of a preservative, 0.5%-2% of a lubricant and 0.2%-0.5% of a thickener, the composite black nano pigment is prepared by compounding carbon black, iron oxide black and graphene carbon quantum dots according to the mass ratio of (3-7): (1-4): (1-4), organic molecules containing multiple conjugated structures are selected as the light absorption enhancer, and after the light absorption enhancer and the composite pigment have a synergistic effect, the blackness of the ink is further improved, and the ink has a good application prospect. And the chemical stability of the light absorption enhancer ensures that the light absorption enhancer is effective in ink for a long time.

Description

Technical Field

[0001] This invention belongs to the field of stationery manufacturing technology, specifically relating to a high-performance ink formula and preparation process suitable for ballpoint pens, and more specifically, to a super black ballpoint pen ink composition and ballpoint pen refill with ultra-high blackness, excellent lightfastness, water resistance, smooth writing performance and wide environmental adaptability. Background Technology

[0002] Neutral pens, also known as gel pens or rollerball pens, have gradually replaced traditional fountain pens and ballpoint pens since their introduction in the late 20th century due to their smooth writing, clear ink, and quick drying, becoming the mainstream writing tool for daily writing, office work, and artistic creation. Current neutral pen ink typically consists of the following components: black pigment or dye to provide color, water-based solvent to adjust flow, thickener to control viscosity, surfactant to improve wettability, and small amounts of preservatives and pH adjusters to ensure storage stability.

[0003] Although ballpoint pen ink technology is relatively mature, with the diversification and increasing sophistication of user needs, existing ink formulations still reveal several technical bottlenecks, as follows: 1. Limitations of Insufficient Blackness: Black gel pen inks typically use carbon black as the primary colorant, or are supplemented with black dyes (such as Acid Black No. 1 or Direct Black No. 19). However, limited by the dispersion of pigment particles and the optical absorption characteristics of dyes, the blackness (expressed as optical density OD value) of traditional inks is usually between 1.2 and 1.5. While this blackness is sufficient for everyday writing needs, in high-end applications (such as calligraphy, legal document signing, or high-contrast printing proofreading), users demand greater visual impact and depth of the ink. Existing single-pigment or dye systems struggle to overcome this blackness bottleneck, and the addition of high-concentration pigments often increases ink viscosity, affecting writing smoothness.

[0004] 2. Insufficient lightfastness and water resistance: The dyes in traditional inks are prone to photochemical decomposition under ultraviolet light, leading to ink fading. While carbon black pigments have good lightfastness, their unmodified surfaces are susceptible to oxidation and will still fade with prolonged exposure to air. Furthermore, most existing inks are water-based, making the ink easily dissolve or spread upon contact with water, especially in humid environments, severely threatening document preservation. Commonly available black gel pen inks exhibit ink diffusion rates as high as 30%–50% in water immersion tests, failing to meet archival preservation requirements.

[0005] 3. The contradiction between writing smoothness and stability: The smoothness of ink depends on low viscosity and good wetting properties, but low-viscosity ink is prone to leakage or evaporation at the pen tip, leading to ink waste and writing interruptions. To prevent leakage, adding thickeners can increase viscosity, but this often causes the ink to clump at the pen tip or break in the writing line. This technical contradiction between smoothness and stability is the core challenge in the design of ballpoint pen inks.

[0006] In recent years, the industry has proposed some improvement solutions to address the aforementioned problems. For example, increasing the carbon black content and introducing dispersants can improve blackness, but the OD value only increases to 1.6, and the water resistance problem remains unresolved. Others have modified pigments by adding silane coupling agents, but the smoothness of the pigments decreases significantly after prolonged writing, and the blackness is also noticeably insufficient. While these improvements have made progress in some aspects, they have failed to comprehensively address the combined requirements of blackness, weather resistance, and smoothness.

[0007] The performance of gel pen ink directly determines its market competitiveness. Therefore, developing a super black gel pen ink that combines ultra-high blackness, excellent weather resistance, and smooth writing performance is not only of great technological innovation significance, but also has broad market application prospects. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention aims to provide a super black gel pen ink and its preparation method. Through innovative formulation design and preparation process, a super black gel pen ink composition with ultra-high blackness, excellent lightfastness, water resistance, and smooth writing performance is provided. This objective is achieved through the following technical solution: As a first aspect of the present invention, a super black neutral pen ink composition is provided, the ink composition comprising 15%–25% composite black nano-pigment, 1%–3% light absorption enhancer, 5%–10% dispersant, 50%–80% aqueous solvent, 1%–3% hydrophobic crosslinking agent, pH adjuster, preservative, lubricant, and thickener, wherein the composite black nano-pigment is prepared by compounding carbon black, iron oxide black, and graphene carbon quantum dots in a mass ratio of 3–7:1–4:1–4; the pH value of the ink composition is in the range of 7–9; the super black neutral pen ink composition is tested at 25°C and a shear rate of 1.256 s. -1 The viscosity at that time was 1000-2000 mPa·s.

[0009] The components are explained as follows: The composite black nano-pigment is an innovative composite black nano-pigment provided by the present invention. It is prepared by combining carbon black, iron oxide black and graphene quantum dots in a mass ratio of 3~7:1~4:1~4, ensuring that the resulting ink has a high blackness.

[0010] The light absorption enhancer is an organic molecule containing a multi-conjugated structure, selected from 2,5-diphenyl-1,3,4-oxadiazole, UV-329, UV-292, and BASF Tinuvine 1130; 2,5-diphenyl-1,3,4-oxadiazole is further preferred, as its conjugated π-electron system can efficiently absorb light in the 400-700 nm wavelength range. When synergistically combined with the composite pigment, the blackness of the ink is further improved, while the chemical stability of 2,5-diphenyl-1,3,4-oxadiazole ensures its long-term effectiveness in the ink.

[0011] The dispersant is one or more of the following: BYK190, BYK191, BYK2012, TEGO Dispers 755W, Clariant Dispersogen PL30, etc.

[0012] The aqueous solvent is a compound of deionized water and one or more of ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, propylene glycol methyl ether, and glycerin; more preferably, it is composed of deionized water, ethylene glycol, and glycerin in a mass ratio of 60:25:15. Deionized water serves as the main carrier, ethylene glycol reduces the ink's evaporation rate, and glycerin improves low-temperature fluidity and prevents the ink from freezing. Optimization of the solvent system ensures the stability of the ink at different temperatures.

[0013] The hydrophobic crosslinking agent is selected from isocyanate crosslinking agents, including hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate; hexamethylene diisocyanate is preferred, which reacts with the hydroxyl groups in the dispersant during the ink drying process to form a hydrophobic crosslinking network. This network structure endows the ink with excellent water resistance, and the ink remains intact even after prolonged immersion in water.

[0014] The pH adjuster is one or a combination of two of triethanolamine, monoethanolamine, and isopropanolamine; the lubricant is one or a combination of two of aqueous phosphate ester, oleic acid, and chlorinated paraffin; and the thickener is one or a combination of two of polysaccharides, cellulose, inorganic thickeners, and alkali-swellable thickeners.

[0015] The pH adjuster is triethanolamine, added at a rate of 0.3% to 1.0%, to control the pH value of the ink at 7-9, ensuring the chemical stability of the pigment and polymer; the lubricant is one of water-based phosphate ester, oleic acid, or chlorinated paraffin; the preservative is an isothiazolinone compound (such as methylisothiazolinone); and the thickener is xanthan gum.

[0016] As a second aspect of the present invention, a method for preparing super black gel pen ink is provided, comprising the following steps: S1. Preparation of composite black nano pigment: Carbon black, iron oxide black and graphene quantum dots are mixed in a mass ratio of 3~7:1~4:1~4, ethanol is added, and after grinding, the mixture is dispersed in an ultrasonic cleaner to obtain a composite pigment suspension with a particle size D50 of 50-75nm. The suspension is concentrated by centrifugation and then used for later use. S2. Preparation of ink base solution: Under stirring conditions, heat the aqueous solvent, add the dispersant, stir to dissolve, then slowly add the light absorption enhancer and hydrophobic crosslinking agent, and continue stirring to form a uniform and transparent base solution; S3. Slowly add the composite pigment suspension prepared in step S1 to the ink base liquid in step S2, disperse it in a high-speed shear disperser, and then add lubricant, preservative, pH adjuster and thickener in sequence, and continue stirring to obtain crude ink. S4. Filtration and post-processing: Filter and degas the crude ink film obtained in step S3 to obtain the final super black gel pen ink.

[0017] As a third aspect of the invention, a ballpoint pen refill is provided, comprising a refill tube and ink filled in the refill tube, said ink being the super black ballpoint pen ink composition described in the first aspect.

[0018] Compared with the prior art, the beneficial effects of the technical solution of this application include: 1. The super black gel pen ink composition provided by the present invention has ultra-high blackness: the blackness (OD value) of the ink reaches 1.8-2.3, which exceeds the limit of traditional inks and provides the ultimate visual effect.

[0019] 2. The super black gel pen ink composition provided by the present invention has excellent lightfastness and water resistance: the ink remains stable under strong light irradiation and water immersion conditions, meeting the requirements for long-term preservation.

[0020] 3. The super black gel pen ink composition provided by this invention achieves a balance between smooth writing and stability: it provides a writing experience without broken lines or leakage under different writing speeds and environmental conditions.

[0021] 4. The super black gel pen ink composition provided by the present invention has wide environmental adaptability: the ink can maintain stable performance in a temperature range of -20℃ to 50℃ and a humidity range of 20% to 90%. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1The examples and comparative examples show a color comparison. From left to right, they are Examples 1-10 and a commercially available super black ink. Detailed Implementation

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0026] In some embodiments of the present invention, an ink composition is provided, comprising 15%–25% composite black nano-pigment, 1%–3% light absorption enhancer, 5%–10% dispersant, 50%–80% aqueous solvent, 1%–3% hydrophobic crosslinking agent, pH adjuster, preservative, lubricant, and thickener. The composite black nano-pigment is prepared by combining carbon black, iron oxide black, and graphene carbon quantum dots in a mass ratio of 3–7:1–4:1–4. The pH value of the super black neutral pen ink composition is in the range of 7–9; and it is prepared at 25°C with a shear rate of 1.256 s. -1 The viscosity at that time was 1000-2000 mPa·s.

[0027] Among them, high-pigment carbon black (specific surface area 200-300 m²) is selected. 2 / g (particle size 10-20 nm) to provide basic blackness and high hiding power.

[0028] Iron oxide black: As an auxiliary pigment, it has excellent chemical stability, and its lightfastness and oxidation resistance are significantly higher than those of carbon black alone. Moreover, its particle size is controlled at 15-25 nm, which matches that of carbon black.

[0029] Graphene quantum dots: with a diameter of 5-10 nm, they have extremely high electron cloud density and light absorption capacity, and enhance the absorption efficiency of ink in the visible light range through quantum size effect.

[0030] During the preparation process, the three materials are combined using wet ball milling and ultrasonic dispersion techniques to ensure a uniform particle size distribution (D50 of 50-75 nm) in the composite pigment suspension. The blackness of the composite pigment far exceeds that of single carbon black, with an OD value exceeding 1.9.

[0031] In some embodiments of the present invention, the light absorption enhancer is an organic molecule containing multiple conjugated structures, selected from 2,5-diphenyl-1,3,4-oxadiazole, UV-329, UV-292, and BASF Tinuvine 1130.

[0032] In some embodiments of the present invention, the dispersant is one or more of BYK190, BYK191, BYK2012, TEGO Dispers755W, and Clariant Dispersogen PL30.

[0033] In some embodiments of the present invention, the aqueous solvent system is a compound of deionized water and one or more of ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, propylene glycol methyl ether, and glycerin.

[0034] In some embodiments of the present invention, the hydrophobic crosslinking agent is selected from isocyanate crosslinking agents, including hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate.

[0035] In some embodiments of the present invention, the pH adjuster is one or a combination of two of triethanolamine, monoethanolamine, and isopropanolamine; the lubricant is one or a combination of two of aqueous phosphate ester, oleic acid, and chlorinated paraffin; and the thickener is one or a combination of two of polysaccharides, cellulose, inorganic thickeners, and alkali-swellable thickeners. Further, the thickener is xanthan gum.

[0036] In some embodiments of the present invention, the method for preparing super black gel pen ink includes the following steps: S1. Preparation of composite black nano-pigment: Carbon black, iron oxide black, and graphene quantum dots were mixed at a mass ratio of 3~7:1~4:1~4, and ethanol was added (solid-liquid ratio 0.5~1:3~5). The mixture was ground in a planetary ball mill and then dispersed in an ultrasonic cleaner to obtain a composite pigment suspension with a particle size D50 of 50-75 nm. The suspension was concentrated by centrifugation and then used for later use.

[0037] S2. Preparation of ink base solution: Under stirring conditions (300 rpm), deionized water, ethylene glycol, and glycerin are mixed in proportion, heated to 50°C, and a dispersant is added. The mixture is stirred and dissolved for 1 hour. Subsequently, a light absorption enhancer and a hydrophobic crosslinking agent are slowly added, and stirring is continued for 2 hours to form a uniform and transparent base solution.

[0038] S3. Slowly add the composite pigment suspension prepared in step S1 to the base liquid in step S2, and disperse it in a high-speed shear disperser at 8000 rpm for 30 minutes to ensure uniform distribution of pigment particles and no obvious precipitation in the system. Then add lubricant, preservative, pH adjuster, and thickener in sequence, and continue stirring for 1 hour to obtain crude ink.

[0039] S4. Filtration and Post-treatment: The crude ink is filtered through a 500-mesh filter membrane to remove large particulate impurities, and then degassed in a vacuum degasser for 30 minutes to remove dissolved gases, thus obtaining the final super black gel pen ink.

[0040] The blackness (OD value) of the super black gel pen ink of this invention is detected using an optical densitometer. The ink is evenly coated onto white paper with a coating stick. After natural drying, the optical densitometer is zeroed using uncoated white paper. The measuring head is then aligned with the coated ink area, the measurement button is pressed, and the OD value is displayed on the screen. The reading is then obtained. (Note: Repeated measurements are taken in different areas of the ink, and the average value is taken to improve accuracy.) Lightfastness is tested using a UV aging chamber with a light intensity of 1.0 W / m². 2 The light exposure time was 300 hours. The stability test was conducted by storing the product at 50°C for 10 days, followed by marking 300 meters of line with an automatic marking machine to observe whether single-sided line breakage occurred.

[0041] Preparation Example Carbon black, iron oxide black, and graphene quantum dots were mixed in a mass ratio of 5:3:2, and ethanol was added (solid-liquid ratio 1:5). The mixture was then ground in a planetary ball mill at 500 rpm for 4 hours, followed by dispersion in an ultrasonic cleaner (frequency 40 kHz, power 300 W) for 30 minutes to obtain a composite pigment suspension with a particle size D50 of 50-75 nm. The suspension was concentrated by centrifugation and then used for later use.

[0042] Water-soluble solvent: It is prepared by mixing deionized water, ethylene glycol and glycerin in a mass ratio of 60:25:15.

[0043] Example 1: Composite black nano pigment (5:3:2) 15% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK190 5% Water-based solvents 75.8% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% 1% aqueous phosphate Xanthan gum 0.4%.

[0044] Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.29, and the viscosity was 1721 mPa·s. The OD value of the ink was 1.79. When filled into a pen refill, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0045] Example 2: Composite black nano pigment (5:3:2) 15% UV-329 1% BYK190 5% Water-based solvents 75.8% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% 1% aqueous phosphate Xanthan gum 0.4% The above formula was followed to produce the finished ink. The ink's pH was measured to be 8.34 and its viscosity to be 1812 mPa·s. The ink's OD value was 1.75. When filled into pen refills, the ink wrote smoothly. After 300 hours of exposure to a UV aging chamber, the ink's OD value showed no significant change. Immersing the ink in deionized water for 24 hours showed no smudging or diffusion. A 300-meter line was drawn on an automatic line marking machine without any single-sided line breakage. After 10 days of heat storage at 50°C, a 300-meter line was drawn on an automatic line marking machine without any single-sided line breakage. A comparison with Example 1 shows that 2,5-diphenyl-1,3,4-oxadiazole has a better blackening effect than UV-329.

[0046] Example 3: Composite black nano pigment (5:3:2) 15% BASF Tinuvine 1130 1% BYK190 5% Water-based solvents 75.8% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% 1% aqueous phosphate Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.33, and the viscosity was 1745 mPa·s. The OD value of the ink was tested to be 1.76. When filled into a pen refill, the ink wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0047] Example 4: Composite black nano pigment (5:3:2) 20% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK190 5% Water-based solvents 70.8% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% 1% aqueous phosphate Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The pH of the ink was measured to be 8.32, the viscosity to be 1745 mPa·s, and the OD value to be 1.92. When filled into pen refills, the ink wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0048] Example 5: Composite black nano pigment (3:4:3) 20% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK20126% 70.5% aqueous solvent 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.29, and the viscosity was 1795 mPa·s. The OD value of the ink was 1.90. When filled into a pen refill, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0049] Example 6: Composite black nano pigment (7:2:1) 20% 2,5-Diphenyl-1,3,4-oxadiazole 2% BYK20126% 69.5% of water-based solvents 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.12, and the viscosity was 1771 mPa·s. The OD value of the ink was tested to be 1.98. When filled into pen refills, the ink wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0050] Example 7: Composite black nano pigment (5:1:4) 25% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK20126% 65.5% water-based solvent 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.34, and the viscosity was 1668 mPa·s. The OD value of the ink was 2.22. When filled into a pen refill, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0051] Example 8: Composite black nano pigment (5:1:4) 25% 2,5-Diphenyl-1,3,4-oxadiazole 1% TEGO Dispers 755W8% Water-based solvent 63.5% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.25, and the viscosity was 1701 mPa·s. The OD value of the ink was 2.26. When filled into a pen refill, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0052] Example 9: Composite black nano pigment (5:1:4) 25% 2,5-Diphenyl-1,3,4-oxadiazole 1% TEGO Dispers 755W8% Water-based solvent 63.5% Toluene diisocyanate 1% Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.23, and the viscosity was 1745 mPa·s. The OD value of the ink was tested to be 2.25. When filled into pen refills, the ink wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0053] Example 10: Composite black nano pigment (7:2:1) 25% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK20126% 70.5% aqueous solvent Isophorone diisocyanate 1% Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.06, and the viscosity was 1789 mPa·s. The OD value of the ink was 2.19. When filled into a pen refill, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0054] Test example The colors of Examples 1-10 and a commercially available super black ink were compared by scratching.

[0055] A scratch test is conducted using color identification paper to compare differences in gloss, hue, and hiding power among ink samples. The specific method is as follows: Place the ink to be tested on the identification paper, with adjacent inks approximately one centimeter apart. Use a scraper to forcefully spread the thin application at a near-perpendicular angle to the identification paper, and then quickly spread the thick application at a slight angle. After the ink surface dries, observe the hue of the thin application, assess the hiding power and transparency of the black bands, and determine the difference in gloss and observe the overall color appearance of the thick application. Typically, white scraping paper is used for black and colored inks, while black scraping paper is used for white ink. Results are as follows: Figure 1 As shown, the blackness of Examples 4-10 of the present invention is significantly better than that of Examples 1-3 and commercially available super black ink, and has a deeper visual effect.

[0056] Comparative Example 1 Composite black nano pigment (2:5:6) 25% 2,5-Diphenyl-1,3,4-oxadiazole 1% BYK20126% 70.5% aqueous solvent Isophorone diisocyanate 1% Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.06, and the viscosity was 1745 mPa·s. The ink's OD value was 2.21. When filled into a pen refill, it wrote smoothly. After 300 hours of exposure to a UV aging chamber, the ink's OD value showed no significant change. Immersing the ink in deionized water for 24 hours showed no smudging or diffusion. No single-sided line breakage was observed when drawing 300 meters of line on an automatic line-drawing machine. However, in the stability test, after 10 days of heat storage at 50℃, severe single-sided line breakage occurred when drawing 300 meters of line on an automatic line-drawing machine. The reason for this is that graphene quantum dots have a graphene-like sheet structure, but are in a nanoscale two-dimensional sheet form with functional groups such as carboxyl and hydroxyl groups at the edges. Furthermore, the sheet structure results in a large specific surface area, strong van der Waals forces and π-π stacking interactions, easily leading to multi-layer stacking and aggregation. Therefore, as their content increases, dispersion becomes difficult, resulting in precipitation and aggregation during the stability heat storage test, leading to poor line drawing.

[0057] Comparative Example 2 Composite black nano pigment (7:2:1) 20% 2,5-Diphenyl-1,3,4-oxadiazole 2% BYK20126% Aqueous solvent (mass ratio 65:30:5) 69.5% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% Oleic acid 0.3% Xanthan gum 0.4% Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.12, and the viscosity was 1798 mPa·s. The ink's OD value was 1.98. When filled into pen refills, it wrote smoothly. After 300 hours of exposure to a UV aging chamber, the ink's OD value showed no significant change. Immersing the ink in deionized water for 24 hours showed no smudging or diffusion. Drawing a 300-meter line on an automatic line marking machine showed no single-sided line breakage. After 10 days of heat storage at 50℃, drawing a 300-meter line on an automatic line marking machine also showed no single-sided line breakage. However, the cap removal performance was not as good as that of a mixture of deionized water, ethylene glycol, and glycerin in a mass ratio of 60:25:15, and after 72 hours of cap removal and storage, the ink became unreadable.

[0058] Comparative Example 3 Composite black nano pigment (5:3:2) 15% BYK190 5% Water-based solvents: 76.8% 1% hexamethylene diisocyanate Triethanolamine 0.7% Methylisothiazolinone 0.1% 1% aqueous phosphate Xanthan gum 0.4%.

[0059] Following the above formula and steps, the ink was made into a finished product. The measured pH of the ink was 8.29, and the viscosity was 1745 mPa·s. The OD value of the ink was 1.59. When filled into pen refills, it wrote smoothly. After being exposed to UV aging chamber for 300 hours, the OD value of the ink did not change significantly. When the ink was immersed in deionized water for 24 hours, there was no smudging or diffusion. When a 300-meter line was drawn on an automatic line marking machine, there was no single-sided line breakage. After being stored at 50℃ for 10 days, a 300-meter line was drawn on an automatic line marking machine, and there was no single-sided line breakage.

[0060] In summary, this invention significantly improves the blackness and weather resistance of ink by combining composite black nano-pigments of carbon black, iron oxide black, and graphene carbon quantum dots, supplemented with light absorption enhancers. The addition of hydrophobic crosslinking agents gives the ink excellent water resistance, solving the problem of insufficient blackness in ballpoint pen ink, while also providing excellent writing smoothness.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A super black gel pen ink composition, characterized in that, It contains 15%–25% composite black nano-pigment, 1%–3% light absorption enhancer, 5%–10% dispersant, 50%–80% aqueous solvent, 1%–3% hydrophobic crosslinking agent, pH adjuster, preservative, lubricant and thickener, wherein the composite black nano-pigment is prepared by compounding carbon black, iron oxide black and graphene carbon quantum dots in a mass ratio of 3–7:1–4:1–4.

2. The super black gel pen ink composition according to claim 1, characterized in that, The super black neutral pen ink composition has a pH range of 7-9; at 25°C and a shear rate of 1.256 s⁻¹, it can withstand temperatures of 15°C and 1.256 s⁻¹. -1 The viscosity at that time was 1000-2000 mPa·s.

3. The super black gel pen ink composition according to claim 1, characterized in that, The composite black nano-pigment was prepared by the following method: Carbon black, iron oxide black, and graphene quantum dots were mixed in a mass ratio of 3~7:1~4:1~4, ethanol was added, and the mixture was ground in a ball mill and then ultrasonically dispersed to obtain a composite pigment suspension with a particle size D50 of 50-75nm. The suspension was then concentrated by centrifugation and used for later use.

4. The super black neutral pen ink composition according to claim 1, characterized in that, The light absorption enhancer is an organic molecule containing multiple conjugated structures, selected from 2,5-diphenyl-1,3,4-oxadiazole, UV-329, UV-292, and BASF Tinuvine 1130; more preferably 2,5-diphenyl-1,3,4-oxadiazole.

5. The super black gel pen ink composition according to claim 1, characterized in that, The dispersant is one or more of BYK190, BYK191, BYK2012, TEGO Dispers 755W, and Clariant Dispersogen PL30.

6. The super black gel pen ink composition according to claim 1, characterized in that, The aqueous solvent system is a compound of deionized water and at least one of ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, propylene glycol methyl ether, and glycerin.

7. The super black neutral pen ink composition according to claim 1, characterized in that, The hydrophobic crosslinking agent is selected from isocyanate crosslinking agents, including hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate.

8. The super black gel pen ink composition according to claim 1, characterized in that, The pH adjuster is one or a combination of two of triethanolamine, monoethanolamine, and isopropanolamine; the lubricant is one or a combination of two of aqueous phosphate ester, oleic acid, and chlorinated paraffin; and the thickener is one or a combination of two of polysaccharides, cellulose, inorganic thickeners, and alkali-swellable thickeners.

9. A method for preparing super black gel pen ink, characterized in that, Includes the following steps: S1. Preparation of composite black nano pigment: Carbon black, iron oxide black and graphene quantum dots are mixed in a mass ratio of 3~7:1~4:1~4, ethanol is added, and the mixture is ground and then ultrasonically dispersed to obtain a composite pigment suspension with a particle size D50 of 50-75nm. The suspension is concentrated by centrifugation and then used for later use. S2. Preparation of ink base solution: Under stirring conditions, heat the aqueous solvent, add the dispersant, stir to dissolve, then slowly add the light absorption enhancer and hydrophobic crosslinking agent, and continue stirring to form a uniform and transparent base solution; S3. Slowly add the composite pigment suspension prepared in step S1 to the ink base liquid in step S2, disperse it in a high-speed shear disperser, and then add lubricant, preservative, pH adjuster and thickener in sequence, and continue stirring to obtain crude ink. S4. Filtration and post-processing: Filter the crude ink film obtained in step S3 and degas it to obtain super black gel pen ink.

10. A gel pen refill, the gel pen refill comprising a refill tube and ink filled in the refill tube, characterized in that, The ink is the super black gel pen ink composition according to any one of claims 1 to 8.

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