Ink composition with enhanced viscosity performance across varied environmental conditions

Abstract

The present disclosure relates to an ink composition incorporating colloidal nanoparticles, such as polystyrene, to enhance viscosity stability and performance under varying environmental conditions, particularly within a temperature range of 0°C to 60°C. The colloidal nanoparticles improve the rheological properties of the ink, ensuring smooth flow, consistent application, and preventing issues such as smudging, clogging, and aggregation. The ink composition comprises a colorant, a dispersing agent, a liquid medium, and additives, providing chemical stability, uniform dispersion, and long-term storage reliability. This composition is suitable for various writing and printing applications under diverse environmental conditions.

Description

DescriptionTitle of Invention: Ink Composition with EnhancedViscosity Performance Across Varied Environmental ConditionsTechnical Field

[0001] The present disclosure generally relates to enhancing the viscosity adaptability of ink under diverse environmental conditions, particularly temperature variations, by incorporating polystyrene colloidal nanoparticles into the ink composition.Background Art

[0002] Writing instruments such as pens, markers, and other stationery items are essential tools used in various fields, including education, office work, art, and home applications. The performance and quality of these tools are directly influenced by the ink they contain. Ink plays a pivotal role in determining the functionality and quality of writing instruments, as its absence or poor quality renders these tools ineffective. Moreover, ink behavior is highly sensitive to environmental factors such as temperature, humidity, and pressure, which can significantly impact its performance, especially in real-world usage conditions that deviate from standard testing environments.

[0003] Environmental variations, such as changes in temperature and humidity, can result in common ink-related issues. For example, high temperatures can reduce viscosity, leading to smudging, excessive ink flow, and clogging, while low temperatures can increase viscosity, causing insufficient ink flow, skipping, or irregular patterns. These challenges significantly impact the reliability and usability of writing instruments, limiting their performance across diverse environmental conditions. The quality of ink is a critical factor for manufacturers and brands, as substandard ink can lead to issues like premature drying or leaving unsatisfactory marks on various surfaces such as paper. Ink typically comprises two primary components: pigments or dyes that provide color and a solvent that acts as the matrix. Depending on their compositions, inks can be classified into dye-based or pigment-based categories, with each offering distinct properties. The colorants used in inks can be derived from organic, inorganic, natural, or synthetic sources, iproduced in various scales, including nano and micro, to meet specific performance requirements.

[0004] Various articles and patents have disclosed ink compositions utilizing different particles or production methods, primarily aimed at improving viscosity adaptability over time. However, no existing solution adequately addresses the challenge of maintaining ink viscosity stability across a wide temperature range, such as 0°C to 60°C. This limitation significantly restricts the functionality of current ink compositions in applications requiring consistent performance under diverse environmental conditions.Summary of Invention

[0005] This summary is intended to provide an overview of the subject matter of the exemplary embodiments of the present disclosure, and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed implementations. The proper scope of the exemplary embodiments of the present disclosure may be ascertained from the claims set forth below in view of the detailed description below and the drawings.

[0006] In one general aspect of the present disclosure, an ink composition is provided that includes a colorant, a dispersing agent, a liquid medium, and a plurality of additives, and colloidal nanoparticles. The colloidal nanoparticles configured to enhance the viscosity adaptability of the ink when exposed to varying environmental conditions, particularly within a temperature range of 0°C to 60°C.

[0007] The above general aspect may include one or more of the following features. In some exemplary embodiments, the colloidal nanoparticles are made of thermoplastic polymers and are present in the ink composition in amounts ranging from 0.01 wt% to 1 .5 wt%. These particles have a size distribution between 50 nm and 150 nm, ensuring their optimal dispersion and functionality within the composition. The colloidal nanoparticles can be selected from materials such as polystyrene, cellulose, starch, polyethylene oxide, or polyvinyl alcohol, which contribute to enhance the viscosity stability and performance of the ink.

[0008] In one aspect of the present disclosure, the colorant in the ink composition may be sourced from either organic or inorganic materials. The colorant is dispersed ordissolved in the liquid medium, forming a uniform mixture suitable for ink applications.

[0009] In another aspect of the present disclosure, the dispersing agent ensures the uniform distribution of the colorant within the liquid medium and supports the even dispersion of colloidal nanoparticles throughout the ink. This consistent distribution guarantees reliable performance during both use and storage, even under varying environmental conditions. While colloids are inherently stable due to their intrinsic properties, the dispersing agent provides additional benefits by preventing sedimentation or aggregation of both colloidal and non-colloidal colorant components. This dual function ensures a consistent composition and performance of the ink during storage and use, particularly under fluctuating environmental conditions.

[0010] In another aspect of the present disclosure, the liquid medium in the composition can include an organic solvent, an inorganic solvent, or an oil-based solvent. Additionally, the plurality of additives incorporated in the ink composition may include at least one of antioxidants, oleic acids, resins, polymers, metals, binders, crosslinkers, plasticizers, surfactants, stabilizers, or combinations of these, contributing to the ink’s functional properties and adaptability to different applications.Technical Problem

[0011] Writing instruments using ink often face challenges under varying environmental conditions, particularly temperature fluctuations, which lead to uncontrolled changes in viscosity and inconsistencies in "Ink Lay Down." These fluctuations result in issues such as smudging, blobbing, gooping, skipping, and uneven writing patterns. Increased temperatures reduce viscosity, causing excessive and uncontrolled ink flow, while decreased temperatures increase viscosity, restricting ink flow. These problems significantly impact the reliability and quality of writing instruments, limiting their functional performance in diverse environments.

[0012] Additionally, challenges such as pigment aggregation, sedimentation, and phase separation compromise the stability and shelf life of ink, leading to inconsistent performance over time. The lack of uniform dispersion of inkcomponents further exacerbates these issues, affecting the overall quality and user experience.Solution to Problem

[0013] The present disclosure addresses these challenges by incorporating thermoplastic polymer colloidal nanoparticles, such as polystyrene, into the ink composition. These colloidal nanoparticles are employed in nano and micro scales, ensuring dynamic compatibility and viscosity adaptability under varying environmental conditions. The ink maintains reliable performance across a temperature range of 0°C to 60°C, minimizing issues like smudging, skipping, and blobbing caused by uncontrolled ink flow.

[0014] To prevent the sedimentation of colloidal polystyrene nanoparticles and the resulting phase separation in the ink, stable colloids are employed to achieve a homogeneous dispersion. This is accomplished through advanced mixing and ultrasonic processes, complemented by appropriate surfactants and dispersing agents. These additives enhance stability by reducing surface tension and promoting even distribution of particles within the medium. This comprehensive approach ensures a stable ink composition that resists phase separation, extends shelf life, and maintains consistent performance during prolonged storage.

[0015] The narrow size distribution and spherical morphology of the nanoparticles facilitate their homogeneous dispersion within the ink composition. This prevents nozzle blockages, enhances ink flow, and improves writing quality while reducing the risk of clogging.

[0016] The nanoparticles' high surface area, combined with their thermal sensitivity, enhances interactions with the ink matrix and enables precise viscosity adjustments. This ensures smoother and more consistent ink flow across a range of temperatures.

[0017] Furthermore, the chemical compatibility of polystyrene nanoparticles with ink solvents ensures stability without altering the final color or appearance of the ink. The ability to tailor the ink’s rheological properties and stability through surface modification of nanoparticles adds versatility to the composition, enabling it to meet diverse functional and environmental demands. These innovations collectivelyprovide a significant improvement over prior art compositions, offering a reliable and adaptable solution for high-performance writing instruments.Advantageous Effects of Invention

[0018] The present disclosure offers significant advancements in writing ink composition by incorporating polystyrene colloidal nanoparticles, which minimize viscosity fluctuations and ensure stable performance across a temperature range of 0°C to 60°C. This adaptability addresses issues such as uncontrolled ink flow, smudging, skipping, and blobbing, resulting in smoother and more reliable writing performance.

[0019] The colloidal stability and compatibility of nanoparticles within the ink composition ensure their uniform dispersion, thereby preventing sedimentation, aggregation, and phase separation. This stability enhances the chemical integrity of the ink and preserves its final color, maintaining long-term ink quality. Additionally, the thermal sensitivity of the composition allows for precise viscosity adjustments, ensuring consistent "Ink Lay Down", the controlled and uniform deposition of ink during application. Furthermore, the uniform particle size and spherical morphology contribute to improved flow characteristics, effectively preventing clogging in writing instruments and nozzle blockages, and thereby enhancing overall usability.

[0020] The disclosed ink composition is cost-efficient and scalable for industrial production, as the colloidal nanoparticles achieve high performance even at low concentrations. These features collectively make the ink ideal for diverse environmental and operational demands, providing a significant improvement over conventional composition.Brief Description of Drawings

[0021] The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

[0022] [FIG.1A] shows Emission Scanning Electron Microscope (FESEM) images of the polystyrene colloidal nanoparticles at a magnification of 1 pm.

[0023] [FIG.1 B] shows Emission Scanning Electron Microscope (FESEM) images of the polystyrene colloidal nanoparticles at a magnification of 500 nm.

[0024] [FIG.3] shows X-ray diffraction (XRD) analysis of polystyrene nanoparticles to examine their purity, phase, and chemical composition used in the ink.Description of Embodiments

[0025] The following detailed description is presented to enable a person skilled in the art to make and use the methods and devices disclosed in exemplary embodiments of the present disclosure. For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required to practice the disclosed exemplary embodiments. Descriptions of specific exemplary embodiments are provided only as representative examples. Various modifications to the exemplary implementations will be readily apparent to one skilled in the art, and the general principles defined herein may be applied to other implementations and applications without departing from the scope of the present disclosure. The present disclosure is not intended to be limited to the implementations shown but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.

[0026] In one general embodiment of the present disclosure, an ink composition may comprise a colorant, a dispersing agent, a liquid medium, additives, and colloidal nanoparticles. The colloidal nanoparticles can improve the viscosity adaptability and flow behavior of the ink under varying environmental conditions, including temperature, humidity, and pressure.

[0027] In one embodiment, the ink composition may pertain to either dynamic or nondynamic inks. In a preferred embodiment, the ink composition pertains to dynamic inks. Furthermore, the ink composition may be either dye-based or pigment-based. Dynamic inks are designed for applications where viscosity changes are minimal under fluctuating conditions, ensuring reliable ink flow.

[0028] In one embodiment of the present disclosure, the colloidal nanoparticles may comprise a member of the thermoplastic polymer groups consisting of polystyrene, cellulose, starch, polyethylene oxide, or polyvinyl alcohol. In one preferred embodiment, the colloidal nanoparticles may be polystyrene. In a preferredembodiment, polystyrene is selected for its high chemical stability, compatibility with solvents, and contribution to the ink’s overall rheological performance.

[0029] In one embodiment of the present disclosure, the amount of the colloidal nanoparticles may be in a range of 0.01 wt % to 1.5 wt %. This concentration ensures sufficient dispersion of particles within the ink matrix to maintain stability without negatively impacting the ink’s flow or color properties.

[0030] In one embodiment of the present disclosure, the colloidal particles in a nano or micro scales. In another embodiment, the colloidal nanoparticles may have the size distribution in a range of 50 nm to 150 nm. In one preferred embodiment, the size distribution of the colloidal nanoparticle is in a range of 50 nm to 80 nm. The nano-scale size improves the ink’s uniformity and prevents clogging in writing instruments, such as pen tips and rollerballs.

[0031] In one preferred embodiment, the morphology of the colloidal nanoparticle is spherical, which is shown in FIG. 1A and FIG. 1 B. Spherical morphology ensures smooth ink flow and enhances its interaction with the liquid medium, leading to better performance under varying environmental conditions.

[0032] In one embodiment of the present disclosure, the colloidal nanoparticles may enhance the compatibility of the ink under varying environmental conditions. In one embodiment, the compatibility of the ink may comprise the viscosity adaptability of the ink under varying environmental conditions. This compatibility directly addresses challenges such as smudging and irregular ink flow under different temperature conditions.

[0033] In one embodiment, the varying environmental conditions may comprise humidity, pressure, or temperature. In one preferred embodiment, the varying environmental conditions may comprise temperature, and the varying environmental temperature conditions may include a range of 0°C to 60°C. In this range, the ink composition maintains operational performance, ensuring consistent functionality in writing instruments.

[0034] In one exemplary embodiment of the present disclosure, the uniformity in size and morphology of polystyrene nanoparticles, achieved through synthesis methods such as emulsion polymerization, contributes to a homogeneous distribution of nanoparticles within the ink. This uniform distribution preventsclogging at the pen tip, facilitates smooth, consistent ink flow and resulting in improved writing quality. The ink maintains high performance even under extended use or storage, ensuring long-term reliability.

[0035] In one embodiment of the present disclosure, the viscosity changes of the ink that containing the colloidal nanoparticles may be negligible. Due to the uniform dispersion of these colloidal nanoparticles within the ink composition, the ink’s viscosity is maintained under various environmental conditions, particularly varying temperature conditions. This stability ensures reliable ink laydown and prevents performance fluctuations due to temperature variations.

[0036] In one embodiment of the present disclosure, to achieve uniform dispersion of the colloidal nanoparticles within the ink composition, a mixer was initially used and followed by an ultrasonic device during the production process. This dual-step mixing method optimizes particle distribution and enhances ink stability.

[0037] In another embodiment of the present disclosure, uniform dispersion of the colloidal nanoparticles the prevention of phase separation, due to the compatibility between the ink composition and the colloidal nanoparticles, as well as the high stability of the colloidal nanoparticles, allow the ink to be stored for extended periods under standard conditions. This prevents degradation of ink performance over time, ensuring prolonged shelf life under standard storage conditions.

[0038] In one embodiment of the present disclosure, the ink composition comprises colloidal nanoparticles, to address the technical challenges of uncontrolled ink viscosity variations and ink flow fluctuations under varying environmental conditions. The ink composition containing colloidal nanoparticles that enhance the adaptability of ink viscosity under varying environmental conditions, thereby ensuring controlled and reliable "Ink Lay Down." The parameter "Ink Lay Down," assuming other variables remain constant, does not experience significant fluctuations under different environmental conditions. This ensures that writing instruments utilizing this type of ink can maintain high-quality stability and consistent functional performance under varying environmental conditions, particularly temperature variations.

[0039] In one embodiment of the present disclosure, the ink composition incorporates colloidal nanoparticles, by maintaining a stable viscosity minimizes undesirablephenomena such as smudging, blobbing, and gooping caused by excessive ink flow at higher temperatures, as well as skipping and irregular writing patterns due to insufficient ink flow at lower temperatures.

[0040] In one embodiment of the present disclosure, the use of colloidal nanoparticles may be due to their high surface-to-volume ratio, colloidal stability, and suitable rheological properties.

[0041] In one embodiment of the present disclosure, the colloidal nanoparticles are utilized in the ink composition may due to their unique technical characteristics. The colloidal state enables effective interaction with the liquid medium of the ink, facilitating homogeneous mixing with solvents and ensuring consistent stability.

[0042] Furthermore, the colloidal nanoparticles dispersion ensures that the component of the ink composition is evenly distributed throughout the liquid medium, preventing aggregation and maintaining a uniform consistency. This property is essential for preserving the physical and chemical integrity of the ink, which directly impacts its performance under varying environmental conditions. By employing the colloidal nanoparticles, the ink composition may achieve a precise and stable composition tailored to meet the technical requirements of consistent viscosity and reliable application.

[0043] In one exemplary embodiment of the present disclosure, polystyrene colloidal nanoparticles are utilized in the ink composition due to their high chemical compatibility with solvents and other ink components. This compatibility ensures that the ink remains chemically stable and does not undergo adverse reactions, thereby enhancing its overall performance and long-term durability.

[0044] In one exemplary embodiment of the present disclosure, the colloidal nanoparticles may appear milky white at high concentrations and nearly colorless at low concentrations. As a result, their inclusion does not alter the final color of the ink, even when used with various dyes and pigments.

[0045] In one embodiment, to address the challenge of pen tip blockages and inconsistent ink flow, the colloidal nanoparticles with a size of less than about 150 nanometers are utilized in the ink composition. These colloidal nanoparticles may ensure smooth passage through pen tips, rollerballs, and other writing instruments without clogging. Moreover, their spherical morphology may enhance the ink flowand facilitate smooth movement across surfaces, improving overall writing performance.

[0046] In one exemplary embodiment of the present disclosure, the surface of polystyrene nanoparticles can be modified with functional groups to adjust interactions with ink components and optimize the ink’s physical properties. This modifiability allows for enhanced control over the ink’s stability, flow behavior, and overall performance.

[0047] In one embodiment of the present disclosure, the ink composition may include a pigment or dye component in the range of 15 wt% to 30 wt%, serving as the primary colorant. In exemplary embodiment, carbon black may be used for black ink, eosin for red, and phthalocyanine blue for blue. These materials may originate from organic or inorganic sources and may be present in either a dissolved or suspended state in specific solvents.

[0048] In one embodiment of the present disclosure, a dispersing agent in the range of 5-20 wt % may be added to facilitate the uniform dispersion of the colorant in the liquid medium. In one exemplary embodiment, alkyl alkanol amides, as a dispersing agent, may assist in maintaining the homogeneity of the ink composition by preventing sedimentation or aggregation of non-colloidal components. The dispersing agent ensures consistent ink performance during use and storage, particularly under varying environmental conditions

[0049] In another aspect of the present disclosure, the dispersing agent plays a key role in achieving a uniform dispersion of colloidal nanoparticles and the colorant within the ink composition. This ensures consistent ink performance during use and storage. While colloidal nanoparticles are inherently stable due to their intrinsic properties and typically do not require additional stabilization, the dispersing agent enhances the uniformity of their distribution in the ink composition. Additionally, the dispersing agent prevents sedimentation or aggregation of non-colloidal colorant components, thereby improving the overall reliability and consistency of the ink composition under various environmental conditions.

[0050] In one embodiment of the present disclosure, the ink composition may comprise a plurality of additives in the range of 5-15 wt% to maintain the chemical stability of the ink and prevent premature drying. In one exemplary embodiment, theplurality of additives may include antioxidants, oleic acids, resins, polymers, metals, binders, crosslinkers, plasticizers, surfactants, stabilizers, or combination thereof to enhance ink performance and prolong its shelf life.

[0051] In one embodiment of the present disclosure, the ink composition may undergo a filtration process after blending to ensure the removal of larger particles. This process may help create a smooth and uninterrupted ink flow, reducing the risk of clogging during application.

[0052] In one embodiment, the enhancement in viscosity adaptability may be directly attributed to the inclusion of colloidal polystyrene nanoparticles with a size distribution of 50 nm to 150 nm, present in the ink in amounts ranging from 0.01 wt% to 1 .5 wt%. The ink composition demonstrates enhanced viscosity adaptability over a temperature range about of 0°C to 60°C. In a preferred embodiment, the ink composition shows controlled viscosity behavior across the range about of 0°C to 60°C.

[0053] The enhancement of the viscosity adaptability of the ink composition containing the polystyrene colloidal nanoparticles is quantitatively demonstrated in the TABLE 1. As shown, the viscosity of the ink composition disclosed in the present disclosure compared to the control ink composition, is calculated at the temperature of 0°C, 21.5°C, 25°C, 40°C, and 60°C. Calculating and evaluating used a kinematic method, as described in detail in the Examples section.

[0054] TABLE 1

[0055] As illustrated in TABLE 1 , the viscosity of the disclosed ink composition decreases by approximately 92.5% between 0°C and 60°C, whereas the control ink exhibits a reduction of over 99.4% in the same temperature range. This demonstrates a significantly improved viscosity retention rate of the disclosed inkcompared to the control. Such predictable and controlled changes in viscosity ensure enhanced stability, enabling consistent performance in practical applications, including writing instruments and inkjet printing systems. These results demonstrate that the disclosed ink composition effectively mitigates the adverse effects of temperature fluctuations on ink performance.

[0056] Based on the obtained results, the viscosity changes of the ink disclosed in the present disclosure, in the temperature range of 0°C to 60°C, show a reduction of approximately 8% to 12% compared to the viscosity changes of the control sample. This approximate value varies depending on the different amounts of polystyrene colloidal nanoparticles incorporated into the ink composition. By carefully adjusting the concentration of these colloidal nanoparticles, the viscosity behavior can be further optimized to meet specific performance requirements.

[0057] In another embodiment, the disclosed ink composition ability to maintain functional viscosity levels across temperature extremes prevents common issues such as smudging, aggregation, and inconsistent ink laydown, which are prevalent in prior art compositions. The incorporation of colloidal nanoparticles enhances not only the ink’s temperature adaptability but also its long-term storage stability, making it suitable for diverse environmental conditions and operational demands. These attributes make the disclosed ink composition suitable for diverse environmental conditions and operational demands, including high-temperature environments and extended storage periods.

[0058] In one exemplary embodiment of the present disclosure, the enhancement of ink viscosity through the addition of polystyrene colloidal nanoparticles may be evaluated using a kinematic method, as described in detail in the “Examples” section. The results of the XRD analysis of the polystyrene colloidal nanoparticles are presented in FIG. 2.Examples

[0059] Example 1 :

[0060] In an exemplary embodiment of the present disclosure, a method for producing high-quality ink incorporating colloidal polystyrene nanoparticles is provided. Initially, a solvent base may be prepared by combining phenoxyethanol (or benzyl alcohol), oleic acid, and alkyl alkanolamine in suitable proportions within a cleanmixing vessel. The proportions may be selected to achieve a solvent composition that provides the desired stability and viscosity for the ink.

[0061] Subsequently, a pigment or dye selected based on the intended ink color may be gradually introduced into the solvent base. The addition of the pigment or dye may be performed within a specified weight range while ensuring continuous agitation to achieve uniform dispersion throughout the solvent base.

[0062] In a further step, colloidal polystyrene nanoparticles may be introduced into the pigment-solvent mixture. The colloidal nanoparticles may be added within a recommended weight range, followed by thorough homogenization or mixing to ensure their even distribution within the ink composition. This step can enhance the dispersion stability and performance characteristics of the ink.

[0063] The resulting mixture may be allowed to cool while maintaining agitation to prevent agglomeration of the nanoparticles. The viscosity of the ink composition can subsequently be adjusted, as required, by varying the proportions of oleic acid or alkyl alkanolamine within their respective ranges to optimize the flow properties of the ink.

[0064] The ink composition may then be subjected to a filtration process to remove any undispersed particles or impurities. Following filtration, the ink may be transferred into airtight containers and stored under appropriate conditions to preserve its quality and ensure long-term stability.

[0065] The disclosed method may result in a high-performance ink composition characterized by consistent viscosity, uniform dispersion of colloidal nanoparticles, and enhanced reliability under various environmental conditions. The inclusion of colloidal polystyrene nanoparticles can contribute to improved stability, prevent sedimentation, and ensure the production of ink suitable for diverse writing and printing applications.

[0066] Example 2

[0067] In an exemplary embodiment of the present disclosure, the viscosity of ink samples was measured using a rotational viscometer, specifically the Brookfield rotational viscometer method. The measurements were conducted at five different temperatures: 0°C, 21.5°C, 25°C, 40°C, and 60°C. Each ink sample contained 0.5 wt% of colloidal polystyrene nanoparticles.

[0068] Rotational viscometers operate by measuring the torque required to rotate an object immersed in a fluid, which correlates with the fluid’s viscosity. The digital readout and ease of use of these viscometers provide high precision and reliable results.

[0069] The results from TABLE 1 demonstrate that the inclusion of colloidal polystyrene nanoparticles in the disclosed ink composition significantly reduced viscosity variations across different temperatures compared to the control sample. The viscosity retention was evaluated by calculating the percentage reduction in viscosity between 0°C and 50°C for both the disclosed ink composition and the control sample. Equation (1 ) illustrates the formula employed for this calculation: X 100 Equation (1 )

[0071] In this context, the "New Value" represents the viscosity at 50°C, and the "Old Value" represents the viscosity at 0°C. For the disclosed ink composition, using Equation 1 , the viscosity reduction was calculated to be approximately 92.5%, while the control sample exhibited a reduction of over 99.4% within the same temperature range. These calculations illustrate that the disclosed ink composition retains a significantly higher proportion of its initial viscosity compared to the control sample, highlighting the stabilizing effect of the colloidal polystyrene nanoparticles. This improved viscosity stability directly contributes to the ink’s reliable performance under varying environmental conditions.

[0072] This demonstrates improved viscosity retention and stability. The results of viscosity measurement of the ink in the temperatures of 0, 21 .5, 25, 40, and 60°C.

[0073] Example 3

[0074] The morphology and size distribution of the colloidal polystyrene nanoparticles used in the ink composition were analyzed using field emission scanning electron microscopy (FESEM). The FESEM images provide critical evidence of the uniformity and spherical morphology of the colloidal nanoparticles, which directly contribute to the enhanced performance of the ink composition.

[0075] FIG. 1A illustrates the uniform size distribution of the polystyrene colloidal nanoparticles at a magnification of 1 pm. The image demonstrates that the colloidal nanoparticles are evenly dispersed and exhibit consistent size distribution, whichis critical for ensuring homogeneity in the ink composition. This uniform dispersion minimizes aggregation and phase separation, thereby enhancing the stability and functional performance of the ink under varying environmental conditions.

[0076] FIG. 1 B further validates the spherical morphology of the colloidal nanoparticles, as seen at a magnification of 500 nm. The spherical morphology of the nanoparticles is advantageous for improving the flow behavior of the ink, as it reduces resistance during movement through narrow passages, such as pen tips or printer nozzles. The smooth surface and consistent shape also facilitate uniform dispersion within the liquid medium, ensuring reliable viscosity stability and ink performance across a range of temperatures.

[0077] The nanoparticles exhibit a size of less than 100 nanometers, as observed in FIG. 1 B, with both uniform size and spherical morphology. The combination of these characteristics significantly contributes to the ink's rheological properties by enabling better interaction with the liquid medium and ensuring the nanoparticles remain well-dispersed within the ink matrix. This dispersion avoids nanoparticle aggregation, maintaining a homogeneous structure that is essential for the stability and functionality of the ink. These features are particularly critical for addressing challenges such as inconsistent ink flow, smudging, and skipping, ultimately enhancing the performance of the ink under various environmental conditions.

[0078] Example 4

[0079] In an exemplary embodiment of the present disclosure, X-ray diffraction (XRD) analysis was conducted to evaluate the structural properties of the colloidal polystyrene nanoparticles used in the disclosed ink composition. As shown in FIG. 2, the XRD spectra confirm that the synthesized nanoparticles are composed of polystyrene. The XRD pattern exhibits a broad peak centered around 29 « 20°, indicative of the molecular arrangement within the polystyrene colloidal nanoparticles. This broad peak suggests a degree of crystallinity arising from the ordered arrangement of molecular chains within the material.

[0080] The structure of the polystyrene nanoparticles plays a critical role in enhancing their stability and compatibility within the ink composition. The properties ensure robust particle integrity and uniform dispersion within the liquid medium, which are essential for maintaining the viscosity stability of the ink across a wide range ofenvironmental conditions. This structural stability reduces the likelihood of aggregation or phase separation, thereby ensuring consistent ink performance during storage and application.

[0081] The XRD results complement the findings from viscosity and morphology analyses, further validating the effectiveness of the colloidal nanoparticles in achieving superior ink properties. By maintaining structural integrity and consistent interaction with the liquid medium, the colloidal polystyrene nanoparticles effectively control ink viscosity over a temperature range of 0°C to 60°C. This ensures reliable performance in writing instruments and printing systems, mitigating issues such as smudging, clogging, or uneven ink flow commonly associated with conventional inks.

[0082] The XRD analysis highlights the unique structural attributes of the colloidal polystyrene nanoparticles, which are integral to the improved viscosity stability and functional performance of the disclosed ink composition. This combination of structural stability, thermal adaptability, and effective viscosity control demonstrates the significant role of the colloidal nanoparticles in addressing the challenges of maintaining consistent ink performance under varying environmental conditions.

[0083] By combining XRD with viscosity and morphology analyses, the present disclosure demonstrates the effectiveness of colloidal nanoparticles, in particular the colloidal polystyrene nanoparticles, in controlling ink viscosity over a wide temperature range. The combined analysis highlights the interplay between the structural stability provided by the phase purity of the nanoparticles, the uniformity in morphology and size, and the resulting enhanced performance of the ink composition under varying environmental conditions.Industrial Applicability

[0084] The ink composition disclosed in this invention demonstrates significant industrial applicability due to its viscosity stability, which ensures reliable performance under varying environmental conditions, including high-temperature printing and long-term storage. The use of colloidal polystyrene nanoparticles not only enhances the ink’s functionality but also supports cost-effective and large- scale production. The affordability, wide availability, and industrial scalability ofpolystyrene make it an excellent choice for enhancing the functionality of ink compositions, supporting cost-effective production and enabling the manufacturing of high-quality inks at an industrial scale. This ink composition is suitable for a wide range of applications, including writing instruments such as ballpoint pens, rollerball pens, markers, and highlighters, as well as stationery items like artistic tools and painting instruments. Additionally, it can be utilized in manual and mechanical printing applications and any other similar tools or materials requiring stable and high-quality inks.

Claims

AMENDED CLAIMS received by the International Bureau on 30 May 2025 (30.05.2025)

1. An ink composition comprising: a colorant, a dispersing agent, a liquid medium, a plurality of additives, and characterized by spherical polystyrene colloidal nanoparticles, wherein the spherical polystyrene colloidal nanoparticles configured to enhance the viscosity stability of the ink in a temperature range of 0°C to 60°C; wherein the spherical polystyrene colloidal nanoparticles present in an amount of 0.01 wt % to 1.5 wt % relative to the total ink composition and having a size distribution in a range of 50 nm to 150 nm.

2. The ink composition according to claim 1, wherein the colorant comprises a pigment or dye selected from organic or inorganic materials, and is suspended or dissolved in the liquid medium.

3. The ink composition according to claim 1, wherein the liquid medium comprises one or more organic or inorganic solvents suitable for use in the ink composition.

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