Photo luminescent toner for developing electrostatic latent images and manufacturing method thereof

Abstract

Provided is an electrophotographic photo toner for electrostatic latent images having fluorescent properties upon UV irradiation, wherein a silica-organic ligand structure or a silica-carbon dot is added to the inside of the toner to be aggregated, surface-treated on the outside of the toner, or treated on both the inside and outside of the toner. The silica-organic ligand structure or silica-carbon dot can be widely used in a wide range of application fields including optoelectronics, light-emitting diodes, chemical and bio-sensing, bio imaging, drug delivery, photo- and electrocatalysts, latent fingerprint detection, and anti-counterfeiting, in addition to the use for surface treatment of toners.

Description

Fluorescent toner for electrostatic latent image development and its manufacturing method

[0001] The present disclosure relates to an electrophotographic photo luminescent toner and a method for manufacturing the same, and more particularly, to a photo luminescent toner for developing electrostatic latent images.

[0002] The electrophotographic process generally includes the following steps: a charging step for uniformly charging the surface of an electrostatic latent image carrier; an exposure step for forming an electrostatic latent image on the charged electrostatic latent image carrier; a developing step for attaching a toner to the latent image to make the latent image visible; a transfer step for transferring a photo luminescent toner to the surface of a recording medium such as paper; a cleaning step for removing toner remaining on the electrostatic latent image carrier; a de-static step for lowering the electrical characteristics of a photosensitive material; and a fixing step for fixing the toner to the recording medium by heat or pressure.

[0003] The two most common methods for producing toner used in standard electrophotographic processes are the pulverized toner method and the polymerized toner method. In the pulverized toner method, the main ingredients—resin, pigment, charge control agent, and release agent—are mixed at a temperature above the softening point of the resin, followed by cooling and pulverization. The advantages of pulverized toner include a wide range of resins and the relative ease of manufacturing the desired toner. However, the disadvantages are that the particle shape and surface structure cannot be intentionally controlled, resulting in irregular particle shapes and a broad particle size distribution. This results in a large surface charge distribution and ultimately lower stability during development and fixation. Furthermore, the process involves heating the components at high temperatures, melting and mixing them, mechanically pulverizing them to the desired particle size, and finally hardening them. This process requires extensive processing and equipment, consumes significant amounts of heat, and suffers from poor energy efficiency, leading to high manufacturing costs.

[0004] Furthermore, particles obtained through mechanical grinding have irregular shapes, which can lead to problems such as reduced fluidity, distribution, and reproducibility of fine dots. Furthermore, irregular toners generally exhibit lower transfer efficiency than spherical toners. Compared to spherical toners, irregular toners are more likely to generate residual toner that transfers to locations other than the paper during the transfer process, and they tend to be uneven and thick overall.

[0005] In addition, there is a disadvantage in that compatibility is low because the interfacial tension between the low molecular weight wax, which is an internal additive, and the high molecular resin used as a binder for the toner is too high, and even if the same type of wax and resin are used, there is a disadvantage in that they do not mix well in a molten state due to the difference in viscosity between the two substances. This has a disadvantage in that even after the melt processing through the extruder, the cooling process, and the toner completion stage through pulverization, classification, and external addition, the mechanical properties of the toner itself are reduced, causing frictional heat due to friction between toner particles in the actual developing device or toner deterioration due to contact friction between developing parts, which ultimately causes instability in the toner charge amount, shortened toner lifespan, and occurrence of image contamination.

[0006] In addition, since wax dispersion is very difficult, there is a limit to increasing the wax content, and if dispersion is not good, the undispersed wax or coloring agent is exposed to the outer surface of the toner by mechanical grinding, so the obtained particles tend to have low charging stability and low preservative properties. In addition, due to the limitations of the mechanical grinding process, toner particles composed only of wax or toner particles lacking wax may be generated, which can cause problems such as image defects such as streaks, decreased fixation characteristics such as offset, and reduced gloss.

[0007] Recently, with the increasing demand for high-resolution and high-performance electronic photography, toner particle sizes and spherical shapes have become increasingly mainstream. Therefore, toners with a narrow particle size distribution of 5-6 micrometers are becoming increasingly popular. However, producing pulverized toner particles of this small size requires significant crushing energy and results in low yields. Therefore, the production of spherical toner particles with small particle sizes is typically achieved through a polymerization process.

[0008] Polymerization toner processes include suspension polymerization, where monomers polymerize in a liquid phase to produce the desired particulate resin, and emulsion polymerization, which coagulates an emulsion to produce particles of the desired size. The advantages of this polymerization process include excellent charge stability and preservative properties, the ability to produce small-diameter toners with a nearly perfect spherical shape, and lower carbon dioxide emissions compared to conventional grinding methods (mixing, kneading, grinding, and classification). Among these, polymerized toners manufactured by the emulsion coagulation process have the advantage of excellent particle shape control, ranging from perfectly spherical to potato-shaped. Spherical toners are transferred to paper with a uniform thickness and concentration and produce less reverse polarity toner, but they are difficult to clean. To compensate for this cleaning disadvantage, the potato-type shape is mainly used.

[0009] Emulsion coagulation is a process that starts with fine particles smaller than 0.5 µm. A resin dispersion and a colorant dispersion are mixed to form coagulated particles of the desired particle size. The coagulated particles are then heated to coalesce. This process offers a wide range of material options and facilitates control over the shape, particle size, particle size distribution, and surface structure of the toner.

[0010] Unlike pulverized toner, this emulsion polymerization method suppresses surface exposure of pigments and waxes through a core-shell structure, contributing to uniformity of charge, fluidity, and thermal stability. Furthermore, this core-shell structure allows for both high gloss and a wide fixation area.

[0011] Recently, efforts have been made to improve the low-temperature fixation of toners due to the trend toward lower energy consumption and faster printing speeds. Methods for achieving this low-temperature fixation, such as lowering the Tg of the resin and encapsulating it with a binder resin with a relatively high Tg, have been proposed. While these methods achieve the goal of low-temperature fixation, they are inadequate for heat storage.

[0012] Therefore, toner is manufactured by using a low molecular weight resin below the critical molecular weight and a high molecular weight resin with a large molecular weight in an appropriate ratio to enable functional separation control. In other words, each resin performs its function independently. The low molecular weight resin below the critical molecular weight exhibits functions in terms of MFT and Gloss due to the absence of entanglement within the molecular chain, while the high molecular weight resin with a large molecular weight has a lot of entanglement, allowing it to maintain a certain elasticity even at high temperatures, thereby contributing to anti-offset properties, enabling the rheology design of the toner to be designed.

[0013] By combining the above conditions, a toner was manufactured that has a wide fixation margin and can respond to changes in printing process speed by controlling the viscoelastic properties of the toner.

[0014] In particular, in order to respond to the recent trend toward full color, high speed, and high image quality of printers, as well as the trend toward miniaturization (light weight) and eco-friendliness, the shape and surface control technology of toner is becoming increasingly important in order to satisfy the physical properties of toner required for the electrophotographic process.

[0015] For example, because the number of times the toner receives shear force from external materials increases due to high speed, a toner design with high durability is required, and to reduce the amount of residual toner after transfer in order to miniaturize and become environmentally friendly, a toner surface treatment technology is required to increase the uniformity of toner charge and improve transfer efficiency.

[0016] To enhance charge stability, transfer efficiency, and cleanability, the selection of an external additive that applies appropriate inorganic particles to the surface is crucial. External additives impart fluidity to the resin particles, improving toner supply and adhering to the toner surface, providing stable charge performance. They also significantly impact cleanability by reducing the surface adhesion of the electrostatic latent image carrier, facilitating the easy removal of residual toner.

[0017] However, inorganic fine particles used as conventional surface treatment agents have difficulty ensuring such uniformity of charge. For example, the commonly used fumed silica-based inorganic fine particles have a strong negative polarity, making them prone to charge-up. To prevent this excessive triboelectric charging, titanium oxide inorganic fine particles are often added. However, titanium oxide has low electrical resistance and good charge exchange properties, making it relatively easy to produce negatively or weakly charged toners, which hinders uniformity of charge. In particular, when silica inorganic fine particles are added, the more porous the silica structure and the more hydrophilic the surface, the more excessively high the chargeability of the negatively charged toner at low temperature and low humidity. On the other hand, at high temperature and high humidity, moisture acts as a kind of conductor, so the more moisture is absorbed, the less chargeability there is, resulting in poor concentration reproducibility, such as a rapid increase in concentration at high temperature and high humidity, and background contamination. In addition, this can cause image stains due to electrostatic effects at low temperature and low humidity.

[0018] Therefore, to solve this environmental charge stability problem, silica or titanium dioxide whose surface has been treated with hydrophobic silicone oil or silica coupling agent is generally used. However, the surface treatment causes the fine particles to coagulate strongly, which reduces the dispersibility of the toner or causes fluidity or blocking. In particular, in the case of the fumed type silica used in the past, silica aggregation often occurs during the manufacturing process, which reduces the performance of the inorganic fine particles. When the dispersibility of these inorganic fine particles is poor, fluidity, caking resistance, and fixation are poor, which often leads to poor toner supply or reduced fixation. In addition, when the silica fine particles aggregate, the cleanability is also reduced, which causes problems such as filming in which the fine particles adhere to the electrostatic latent image carrier or contaminating the charge roller, causing uneven charging of the electrostatic latent image carrier and reduced fixation.

[0019] Especially recently, when using small-diameter toners for high image quality, it is difficult to obtain sufficient performance using these inorganic fine particles. As the toner particle size decreases, powder fluidity deteriorates, so the addition of large amounts of inorganic fine particles is necessary. These external additives are exposed to friction between the supply roller and blade during the electrophotographic process or to stirring within the developer, and thus tend to easily detach from the toner surface or become embedded within the toner surface due to such stress. When the external additives detach or become embedded, the fluidity of the toner decreases, which reduces supplyability and increases adhesion to the developing roller, resulting in a rapid decline in developability and durability.

[0020] To improve the aggragation problem of fumed silica, silicas produced by the sol-gel method are being used. Sol-gel silica is silica obtained by removing the solvent and drying the silica sol suspension produced by hydrolysis and condensation reaction of alkoxy silane in an organic solvent with water in the presence of a catalyst. It is characterized by having the form of a single spherical particle.

[0021] The present invention aims to provide an electrophotographic toner for electrostatic latent imaging having a fluorescent property when irradiated with UV at 365 nm by using a method of injecting a structure produced by silica-organic ligand hybridization into a silica sol manufactured by a conventional sol-gel method, hydrophobicizing the structure, and then drying and crushing the structure to form particles and then coating the structure on the surface of the toner, and a method of injecting carbon dots into a silica sol manufactured by a conventional sol-gel method, hydrophobicizing the structure, and then coating the structure on the surface of the toner.

[0022] Alternatively, an external additive for toner can be manufactured by mixing the above two methods, and another method is to manufacture a toner having fluorescent properties by mixing raw materials, such as binder resin, wax, pigment, and CCA (charge control agent), within the toner.

[0023] The present invention makes it possible to increase luminous efficiency and control the amount of charge through a silica-organic ligand structure, since it is not easy to control the charging characteristics of a toner when only carbon quantum dots are used.

[0024] The present invention provides an electrophotographic toner for electrostatic latent imaging having fluorescent properties upon UV irradiation, wherein a silica-organic ligand structure or a silica-carbon dot is added to the inside of the toner and aggregated, or is surface-treated on the outside of the toner, or is treated on both the inside and outside of the toner.

[0025] The present invention enhances luminescence efficiency and enables charge control through a silica-organic ligand structure, as it is difficult to control the charging characteristics of a toner using only carbon quantum dots. The manufactured fluorescent silica is a new type of silica complex of carbon-based nanomaterials composed only of abundant non-metallic elements such as carbon, oxygen, hydrogen, and nitrogen, unlike existing toxic semiconductor quantum dots such as CdS, CdSe, and CdTe.

[0026] The above fluorescent silica-organic ligand structure or silica-carbon dot is characterized by exhibiting multi-color fluorescence characteristics such as white, blue, yellow, red, and orange when irradiated with 365 nm UV. These toner particles exhibiting multi-color luminescence such as red, green, blue, yellow, and orange can be printed on an electrophotographic printer or multi-function printer to exhibit fluorescence characteristics, and these fluorescence characteristics can be utilized for security, anti-counterfeiting, and authenticity determination.

[0027] The above toner is characterized by exhibiting a maximum fluorescence intensity of 461 nm for blue, 521 nm for green, and 620 nm for red at an excitation light wavelength of 400 nm through photoluminescent analysis.

[0028]

[0029] 1) Silica manufacturing

[0030] In addition, we used silica manufactured in a sol-gel type with a narrow particle size distribution that allows for size control of various silica particles while maintaining the basic characteristics of toner such as charging, developing, transfer, and fixing, and it has the advantage of easy particle size control from 10 nm to 200 nm. In addition, we minimized charging differences depending on the environment by performing hydrophobic silane treatment such as PDMS, HMDS, DMDES, and OTES.

[0031]

[0032] 2) Silica phosphor using carbon dots

[0033] To produce multi-color light emission such as red, green, blue, yellow, and orange, carbon dots were doped with nitrogen or acid-treated, and inorganic nano metal oxide particles with sizes ranging from several nm to several tens of nm were brought into proximity to increase electron mobility, thereby producing various multi-color light-emitting phosphors under UV light.

[0034] The above complex is characterized in that carbon dots having a diameter of 2 to 10 nm are bonded to the surface of carbon quantum dots by providing hydroxyl and carbxyl groups so that they can form clusters with inorganic nanoparticles having a diameter of 2 to 50 nm, and by controlling electrostatic attraction or repulsion and hydrogen bonding with the inorganic nanoparticles.

[0035] In addition, the above complex is characterized by exhibiting red, green, blue, yellow, and orange fluorescence characteristics depending on the content of carbon dots, the content of nitrogen, and the type and size of inorganic nanoparticles when irradiated with 365 nm UV.

[0036] Meanwhile, in the above complex, the carbon dot comprises polysaccharides such as biomass-based cellulose, hemicellulose, and lignin, monosaccharides or disaccharides such as glucose, sucrose, and xylose, and acids such as citric acid, and is characterized in that it is manufactured through a hydrothermal reaction in water using these raw materials as they are or after acid treatment. Biomass-based materials may be selected from the group consisting of pulp materials such as UNP (unbleached kraft pulp), BKP (bleached kraft pulp), and TMP (thermo mechanical pulp), recycled paper materials such as ONP (old news paper), OCC (old corrugated container), OMP (old magazine printing matters), MOP (mixed office paper), and milk cartons, and food-based recycled materials such as starch or citric acid, such as rice bran, coffee grounds, and fruit juice.

[0037] The numerous carboxyl moieties on the CD surface provide excellent water solubility and biocompatibility. These surface moieties enable CDs to act as proton transporters for nanoparticles. CDs are also suitable for chemical modification and surface passivation with various organic, polymeric, inorganic, or biological materials. Surface passivation enhances both the physical properties and the fluorescence properties of CDs.

[0038] Synthetic methods for CDs can be broadly divided into two categories: "top-down" and "bottom-up" methods. These can be accomplished through chemical, electrochemical, or physical techniques. The resulting CDs can be optimized through pre- or post-processing.

[0039] <Synthesis method>

[0040] 1) The "top-down" synthetic route involves the decomposition of larger carbon structures, such as graphite, carbon nanotubes, and nanodiamonds, into CDs using laser ablation, arc discharge, and electrochemical techniques. For example, multi-walled carbon nanotubes (MWCNTs) were grown on carbon paper and then inserted into an electrochemical cell containing a supporting electrolyte containing degassed acetonitrile and 0.1 M tetrabutyl ammonium perchlorate. This method was then applied to cut CNTs or assemble them into functional patterns, demonstrating its versatility in manipulating carbon nanostructures.

[0041] 2) "Bottom-up" synthetic routes involve synthesizing CDs from small precursors such as carbohydrates, citrates, and polymer-silicon nanocomposites via hydrothermal reactions, solvothermal decomposition, pyrolysis, and microwave synthesis. However, microwave synthesis has the disadvantage of uneven heat generation, resulting in inhomogeneous production. Similarly to pyrolysis, its limited capacity results in low carbon quantum dot yields. In contrast, hydrothermal synthesis offers the advantages of high yields and finely controlled temperature and time, making it ideal for optimizing synthesis conditions.

[0042] However, the above top-down or bottom-up method can cause problems in controlling the particle size distribution of CDs if the type of precursor, type of functional group, concentration, manufacturing temperature and time, type of solvent, pH, etc. are not optimized, making it difficult to achieve optimal luminescence efficiency. Therefore, it is important to find the optimal conditions among various synthesis conditions to synthesize carbon quantum dots with the desired characteristics.

[0043] In order to increase the fluorescence intensity and express multi-color, the inorganic nanoparticles used for hybrid are spherical particles of 2 to 50 nm and are characterized by containing one or more components selected from the group consisting of Europium, SiO2, TiO2, ZnO, Fe2O3, CuO, MgO, Mg(OH)2, Al2O3, Nd2O3, Ce2O3, Er2O3, and Dy2O3.

[0044] The above silica-carbon dot is characterized by the carbon dots being uniformly distributed within the silica by adding the carbon dots during the silica manufacturing process.

[0045] Meanwhile, the above silica-carbon dot is characterized by carbon dots bonded on the surface of nanoparticle silica.

[0046]

[0047] 3) Silica-organic ligand structure

[0048] In addition, during the production of silica by the sol-gel method, the silica sol is combined with an organic ligand selected from Carboxylates, Imidazolates, Pyrazolates, Aromatic Ligand, Phosphonates, Triazolates, Porphyrins, and Dipyridyl Ligands to produce a silica-organic ligand structure. Generally, Carboxylates, Imidazolates, Pyrazolates, Aromatic Ligand, Phosphonates, Triazolates, Porphyrins, and Dipyridyl Ligands are used as the organic ligand, and among these, a ligand that easily combines with silica and has fluorescent properties is selectively used to produce a silica-orgainic ligand structure.

[0049]

[0050] 4) Manufacturing of electrostatic latent electrophotographic toner with fluorescent properties

[0051] The toner manufacturing method of the present invention using an organic ligand

[0052] Step for manufacturing silica using sol-gel method;

[0053] A step of structuring by combining the manufactured silica sol with an organic ligand; and

[0054] It is characterized by including a step of adding a silica-organic ligand structure to the inside of the toner or performing surface treatment on the outside of the toner.

[0055]

[0056] Meanwhile, the method for manufacturing a toner using the silica-carbon dot of the present invention

[0057] Step for manufacturing carbon quantum dots (CDs);

[0058] Step for manufacturing silica using sol-gel method;

[0059] A step of surface-treating the manufactured silica particles with carbon quantum dots;

[0060] It includes a step of adding the above silica-carbon dot to the inside of the toner or performing surface treatment on the outside of the toner.

[0061] The above silica-carbon dot complex is characterized in that carbon dots having a diameter of 2 to 10 nm are provided with hydroxyl and carbxyl groups on the surface of the carbon quantum dots so that they can form clusters with inorganic nanoparticles having a diameter of 2 to 50 nm, and are bonded to the inorganic nanoparticles by controlling electrostatic attraction or repulsion and hydrogen bonding.

[0062]

[0063] Another method involves the step of manufacturing carbon quantum dots (CDs);

[0064] Step of adding carbon dots during the production of silica by sol-gel method;

[0065] A step of uniformly distributing carbon dots inside the silica particles;

[0066] It includes a step of adding the above silica-carbon dot to the inside of the toner or performing surface treatment on the outside of the toner.

[0067] The present invention is a technology for expressing fluorescent characteristics from within a pulverized toner or a polymerized toner, a technology for expressing fluorescent characteristics on the surface of the toner, or a technology for designing a toner so as to have both of these characteristics, thereby enabling the toner to additionally express fluorescent characteristics under UV irradiation in addition to the basic characteristics of an existing toner.

[0068] The silica-organic ligand structure or silica-carbon dot structure of the present invention has optical properties with tunable excitation emission, and is highly attractive due to its high photochemical and colloidal stability, excellent biocompatibility, easy-to-use equipment synthesis process, and low raw material cost. As mentioned above, it is composed of only C, N, and O, making it a completely metal-free, eco-friendly material for safe, advanced applications. In addition to its use in surface treatment of toners, this material has been extensively studied in a wide range of applications, including optoelectronics, light-emitting diodes, chemical and biosensing, bioimaging, drug delivery, photo- and electrocatalysis, latent fingerprint detection, and anti-counterfeiting.

[0069] These toners can be used to enhance security in government agencies, research institutes, and companies, and to distinguish between genuine and counterfeit toners. They can also be used in technologies that automatically adjust the developer density by sensing the toner-to-carrier ratio and the amount of toner on the developer or transfer roller via sensors within the printer.

[0070] Figure 1 is a schematic diagram of the chemical structure of a complex formed by structuring silica-organic ligand.

[0071] Figure 2 is a photograph showing the luminescence characteristics of a nanosilica-organic ligand structure sol under UV.

[0072] Figure 3 is a photograph showing the luminescence characteristics of the manufactured colorless fluorescent toner under visible light (left) and UV irradiation (right).

[0073] Figure 4 is a photograph showing the luminescence characteristics when a portion of an image printed using a home printer after filling a developer with black toner manufactured in Examples 1 to 6 is irradiated with UV.

[0074] To facilitate understanding of the present invention, preferred examples are presented below. However, the following examples are provided solely to facilitate understanding of the invention and are not intended to limit the scope of the present invention.

[0075]

[0076] Example

[0077] 1. Preparation of nano silica particles by sol-gel method

[0078] The sol-gel method using the Stober method is widely used for the production of monodisperse silica. The Stober method involves a condensation reaction between alkyl silicate and silicic acid in the presence of alcohol, using an ammonia catalyst. The particle diameter of silica is determined through the nucleation and growth processes, and the final particle diameter and particle size distribution of the hydrolysis and condensation reactions are determined by the type of precursor, alcohol, ammonia, reaction temperature, and reaction time.

[0079] During the hydrolysis process, the ethoxy group of TEOS (tetraethoxysilane) reacts with water molecules to form an intermediate of Si(OC2H5)4-X(OH)X. Ammonia acts as a basic catalyst and attacks the OH anion of the TEOS molecule, causing hydrolysis to proceed. The chemical reaction can be expressed as follows.

[0080] Si(OC2H5)4+xH20 --> Si(OC2H5)4-X(OH)X+XC2H5OH

[0081] After this reaction, the condensation reaction proceeds immediately and is expressed by the following chemical equation.

[0082] Si(OC2H5)4+ 2H2O --> SiO2+ 4C2H5OH

[0083] TEOS (98% purity) used in the experiment was purchased from Fisher Company, and 31.5% of ammonium hydroxide was purchased from Aldrich Company.

[0084] For the above experiment, TEOS was prepared at 0.2 M, NH3 at 0.2 M, and H2O at 1 M to produce spherical silica particles of approximately 100 nm. After the particles were produced, the silica colloid solution was centrifuged to remove the supernatant, and the remaining silica slurry was washed with ethanol to remove impurities and then dried at 100°C for 2 hours.

[0085]

[0086] 2. Preparation of nanosilica-organic ligand structures

[0087] Organic ligand was dissolved in water at 1% and dispersed at 90°C for 1 hour with high-speed stirring (1000 rpm). The dispersed organic ligand was added to 10 nm silica sol at 1% of the silica solid content and stirred for 30 minutes to proceed with the reaction. The organic ligand reacted on the silica surface, and it was confirmed that the dispersion was maintained in a stable state due to electrostatic repulsion even after long-term standing due to the carboxyl group of the organic ligand.

[0088] The fluorescence characteristics of this nanosilica-organic ligand structure sol with good dispersibility were confirmed at UV 365 nm, and it exhibited blue luminescence characteristics as shown in Fig. 2.

[0089] The above structure was treated with one or more hydrophobic silanes, PDMS, HMDS, OTES, and DMDES, and then dried at 90°C for 24 hours. The dried structure was milled again to produce a final powder and used as a surface treatment agent for toner.

[0090]

[0091] 3. Preparation of carbon dot nano silica particles

[0092] 1) Manufacturing method through continuous process

[0093] During the above sol-gel silica manufacturing process, carbon dots were added to ensure uniform distribution of carbon dots within the silica. 1 mol of distilled water and 0.2 mol of NH3 were stirred at 300 rpm for 10 minutes. The mixture was heated to 48°C and 0.2 mol of TEOS was added dropwise. Carbon dots were added immediately after adding TEOS and aged for 2.5 hours before collecting samples.

[0094]

[0095] 2) Manufacturing method through two-step reaction

[0096] The two-step reaction method first produces nanoparticle silica using a sol-gel process and then proposes a method of bonding carbon dots onto the silica surface. First, 100 nm silica was produced using the above-mentioned nano-silica production method, and the silica solution was treated with N-2(aminoethyl)-3-aminoprophyl trimethoxy silane. The surface charge of the silica solution was confirmed to change positively from -30 mV to +20 mV when measuring the zeta potential due to the amino silane treatment. To the positively changed silica surface, 3% of negatively charged CD was added based on the silica solid. After the addition of CD, the zeta potential was measured to be -10 to +5 mV. The final solution was centrifuged to remove the supernatant, and the remaining particles were dried at 100°C for 2 hours.

[0097]

[0098] 4. Manufacturing of fluorescent polymerization toner

[0099] 1) Manufacturing of L-type latex

[0100] A polymerizable monomer emulsion was prepared by adding a polymerizable monomer mixture (styrene 825 g, n-butyl acrylate 175 g), 30 g of beta-carboxyethyl acrylate (Sipomer, Rhodia), and 17 g of 1-dodecanethiol as a chain transfer agent (CTA) to a 3 L beaker, adding 418 g of an aqueous sodium dodecyl sulfate (Aldrich) solution (2% with respect to water) as an emulsifier, and stirring. A polymerizable monomer emulsion was prepared by slowly adding dropwise 16 g of an initiator ammonium persulfate (APS) and 696 g of an aqueous sodium dodecyl sulfate (Aldrich) solution (0.4% with respect to water) as an emulsifier to a 3 L double jacketed reactor heated to 75°C while stirring. The prepared polymerizable monomer emulsion was slowly added dropwise over 2 hours. The reaction was conducted at a reaction temperature of 75°C for 8 hours. The size of the manufactured resin latex particles was measured by light scattering (Mictotrac) and was 100 to 300 nm.

[0101]

[0102] 2) Production of H-type latex

[0103] A polymerizable monomer emulsion was prepared by adding a polymerizable monomer mixture (styrene 685 g, n-butyl acrylate 315 g), 30 g of beta-carboxyethyl acrylate (Sipomer, Rhodia), and 418 g of an aqueous sodium dodecyl sulfate (Aldrich) solution (2% to water) as an emulsifier to a 3 L beaker and stirring. In a 3 L double jacketed reactor heated to 60°C, 5 g of an initiator, ammonium persulfate (APS), and 696 g of an aqueous sodium dodecyl sulfate (Aldrich) solution (0.4% to water) as an emulsifier were added dropwise over 3 hours while stirring. The reaction was conducted at a reaction temperature of 75°C for 8 hours. The particle size of the manufactured latex was measured by light scattering (Horiba 910) and was 100 to 300 nm.

[0104]

[0105] 3) Preparation of pigment dispersion

[0106] Take 10g of anionic reactive emulsifier (sodium dodecyl sulfate (Aldrich)) and place it in a milling bath together with 60g of carbon black pigment, add 400g of glass beads with a diameter of 0.8~1mm, and mill at room temperature to prepare a dispersion. A ball mill, super mill, ultrasonic disperser, or microfluidizer can be used as the disperser. The pigment dispersion particle size was measured by the light scattering method (Horiba 910) and was 100~200nm. The solid content of the prepared pigment dispersion was 15%.

[0107]

[0108] 4) Manufacturing of fluorescent toner by adding fluorescent silica to the toner

[0109] In a 7L reactor, 3000g of deionized water, 700g of the above latex mixture for cores (mixture of 90% L-type latex and 10% H-type latex), 195g of the above cyan pigment dispersion, and 237g of wax dispersion (parafin system, solid 30.5%) were added, and a mixture of 364g of nitric acid (0.3mol) and 182g of a coagulant (10% polyethyleneimine solution) was added, and silica-organic ligand structure sol (4% solid content) or carbon dot was added at 1% relative to the solid content.

[0110] After stirring at 11,000 rpm for 6 minutes using a homogenizer, 417 g of the latex mixture was additionally added and stirred for another 6 minutes to obtain aggregates of 1.5 to 2.5 μm. The mixture was placed in a 7 L double jacket reactor and the temperature was increased from room temperature to 55 °C at 0.5 °C / min. When the particle size reached approximately 5.0 μm, 442 g of the latex mixture (a mixture of 90% L-LTX and 10% H-LTX) was additionally slowly added over 20 minutes, and when the D50 (Volume) became 5.0 μm, NaOH (1 mol) was added to adjust the pH to 7. When the particle size D50 (Volume) remained constant for 10 minutes, the temperature was increased to 96 °C. After reaching 96℃ and adjusting the pH to 6.0, a secondary coagulated toner having a potato shape of 5.5 to 7.0㎛ was obtained by coagulating for 3 to 5 hours. The coagulated reaction solution was then cooled below Tg, filtered, and the fluorescent toner particles were separated and dried.

[0111]

[0112] 5) Manufacturing of fluorescent toner by external addition of fluorescent silica

[0113] In addition to the method of manufacturing the above silica-organic ligand structure or carbon dot by agglomeration inside the toner, the method of manufacturing the fluorescent toner by treating the external surface of the toner is as follows. First, the fluorescent silica (silica-organic ligand structure or carbon dot) manufactured in Manufacturing Examples 2 and 3 was injected into an external additive (KM-LS2K) at 0.01 to 5 wt% based on the toner base particles on top of the dry toner particles manufactured in the polymerization toner manufacturing method manufactured in Manufacturing Example 4. The input ratios of the fluorescent silica manufactured through Manufacturing Examples 2 and 3 are as shown in Table 1.

[0114] Figure 4 shows the fluorescence characteristics of a portion of an image printed using a home printer after filling a developer with the black toner manufactured in Examples 1 to 6 and irradiating it with UV light. The left photo shows that the difference between the image of the toner with fluorescent silica added and the image of the toner with untreated silica added is indistinguishable when inspected with the naked eye. However, the right photo shows that when the printed image was irradiated with UV light, the image of the toner with fluorescent silica (left) and the image of the toner with untreated silica (right) showed a clear difference, and it could be confirmed that the image exhibited blue fluorescence.

[0115] Method for coating the surface of a toner with fluorescent silica Fluorescent silica 100 nm Fluorescent silica 50 nm Fluorescent silica 10 nm Fluorescent properties Fluorescent color Example 11 ○ Blue Example 22 ○ + Blue Example 31 ○ Blue Example 42 ○ + Blue Example 51 ○ Blue Example 62 ○ + Blue Comparative example 7000X Blue

Claims

1. An electrophotographic toner for electrostatic latent imaging, wherein a silica-organic ligand structure or a silica-carbon dot is added to the inside of the toner and aggregated, or is surface-treated on the outside of the toner, or is treated on both the inside and outside of the toner and then has a fluorescent property when irradiated with UV light.

2. In paragraph 1, An electrostatic latent electrophotographic toner comprising 0.01 to 5 wt% of the silica-organic ligand structure or the silica-carbon dot based on toner particles.

3. In paragraph 1, An electrostatic latent electrophotographic toner characterized in that the fluorescent silica-organic ligand structure or silica-carbon dot exhibits multi-color fluorescence characteristics such as white, blue, yellow, red, and orange when irradiated with 365 nm UV.

4. In paragraph 1 The above toner is an electrostatic latent electrophotographic toner characterized by exhibiting a maximum fluorescence intensity of 461 nm for blue, 521 nm for green, and 620 nm for red at an excitation light wavelength of 400 nm through photoluminescent analysis.

5. In paragraph 1, The above silica-carbon dot is an electrostatic latent electrophotographic toner characterized in that the carbon dots are uniformly distributed inside the silica by adding carbon dots during the silica manufacturing process.

6. In the first paragraph, the silica-carbon dot is an electrostatic latent electrophotographic toner characterized in that the carbon dot is bonded to a surface of nanoparticle silica.

7. An electrostatic latent electrophotographic toner according to claim 1, wherein the silica-organic ligand structure is characterized in that silica sol is combined with an organic ligand selected from Carboxylates, Imidazolates, Pyrazolates, Aromatic Ligands, Phosphonates, Triazolates, Porphyrins, and Dipyridyl Ligands.

8. Step of manufacturing silica using sol-gel method; A step of structuring by combining the manufactured silica sol and organic ligand; and A method for producing an electrophotographic toner having fluorescence characteristics when irradiated with UV at 365 nm, comprising the steps of adding a silica-organic ligand structure to the inside of the toner or surface-treating the outside of the toner.

9. Step of manufacturing carbon quantum dots (CDs); A step for producing silica by sol-gel method; A step of surface-treating the manufactured silica particles with carbon quantum dots; A method for manufacturing an electrostatic latent electrophotographic toner having fluorescent properties when irradiated with UV at 365 nm, comprising the steps of adding the silica-carbon dot to the inside of the toner or performing surface treatment on the outside of the toner.

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