WO2008094003A1

WO2008094003A1 - Black polymerized toner having core-shell structure

Info

Publication number: WO2008094003A1
Application number: PCT/KR2008/000597
Authority: WO
Inventors: Jung Woo Kim; Chang Soon Lee; Woo Cheul Jung; Ji Hoon Lee; Yu Na Kim; Hui Je Lee
Original assignee: Lg Chem, Ltd.
Priority date: 2007-01-31
Filing date: 2008-01-31
Publication date: 2008-08-07
Also published as: KR20080071947A

Abstract

There is provided a black polymerized toner having a core-shell structure. The black polymerized toner is manufactured in a suspension polymerization method; includes a binder resin monomer, a charge control agent, Carbon Black, a molecular weight control agent, a wax, a dispersing agent, a polar grafting agent, a hydrophilic polymer and a pigment; and a hydrophilic polymer forms a polymer membrane in a shell surface. The black polymerized toner may be useful to maximize charge density of the charge control agent in the toner surface by adding a polar grafting agent in the polymerization of toner, and to improve charging characteristics and the polymerization stability of the toner by adding a pigment and a hydrophilic polymer to minimize the reduction in the charge density of the toner by the Carbon Black.

Description

BLACK POLYMERIZED TONER HAVING CORE-SHELL

STRUCTURE

Technical Field

[1] The present invention relates to a black polymerized toner, and more particularly, to a black polymerized toner having excellent charging characteristics and stability, including pigment, polar grafting agent and a hydrophilic polymer.

[2]

Background Art

[3] Generally, a toner represents a colored and charged fine powder that is used for the development of electrophotographs, etc., and it includes a binder resin, a charge control agent, a pigment, wax, etc.

[4] Methods for manufacturing a toner are mainly divided into two groups: a pulverization process and a polymerization process. Among them, the pulverization process means a method for manufacturing a toner by adding additives such as a pigment, a charge control agent, a wax and the like to a binder resin prepared according to an emulsion polymerization, a suspension polymerization, a solution polymerization, bulk polymerization and the like, melt-mixing or extruding the resulting mixture and mechanically pulverizing the mixture. When the toner is manufactured using the pulverization process, the pulverization process has problems that the manufacturing process is complicated and the energy consumption is high since the pulverization process undergoes various operations such as the polymerization, the melt-mixing, the pulverization, etc. Also, since the sizes of toner particles are controlled through the mechanical pulverization process, the charging characteristics and the fixing property of the toner are not uniformly obtained due to the wide grain size distribution and the irregular shapes. In addition, it is necessary to minimize the sizes of the toner particles to a micrometer level so as to form a high-definition image. However, there are limits to the minimization of the sizes of the toner particles when the toner is manufactured using the mechanical pulverization process.

[5] Meanwhile, the polymerization process is a method for manufacturing toner particles through the polymerization reaction without using the mechanical pulverization process. In this case, the polymerization process has an advantage that it is very simple and it is easy to control the size and shape of the toner particles. The polymerization process is sub-divided into an emulsion polymerization process and a suspension polymerization process. Among them, the emulsion polymerization process means a method comprising: previously emulsifying additives such a pigment, a wax, a charge control agent and the like, dispersing the resulting emulsion in water together with monomers to polymerize toner particles. When the toner is manufactured through the emulsion polymerization process, it is advantageous in that it is possible to control the shape and size of the toner particles by adjusting the conditions such as polymerization temperature and polymerization time during the polymerization process. In this case, the emulsion polymerization process has, however, disadvantages that, since very minute particles may be formed at a range of several micrometers in the manufacture of toner, the minute particles may be hazardously introduced into human bodies, and it is difficult to remove surfactants used as an emulsifying agent.

[6] On the contrary, the suspension polymerization process is a method for manufacturing a toner comprising: uniformly dissolving or dispersing monomers and various additives such as a pigment, a wax, a charge control agent and the like to prepare a monomer mixture, introducing the monomer mixture into an aqueous dispersion solution including a dispersing agent, and applying a shear force to polymerize the toner paticles. In this case, the suspension polymerization process has advantages that the manufacturing process is simple, and it is possible to manufacture spherical toner particles which have good charging characteristics and fixing property. Therefore, a toner is manufactured using the suspension polymerization process according to the present invention. However, when the polymerization stability may be deteriorated in the suspension polymerization, the toner particles may not be uniformly formed in shape and size. In this case, the charging characteristics and fixing property may be degraded, and a printing quality may be bad.

[7] Meanwhile, there is recently an increasing demand for an electrophotographic method capable of rapidly printing a large amount of documents as a computer is generally used to make documents and the like. The electrophotographic method includes: uniformly charging a photoconductive drum; forming an electrostatic latent image by exposing the photoconductive drum surface to light; attaching a toner, which is charged with an opposite polarity to the photoconductive drum, to the electrostatic latent image; transferring the toner forming an image to a transfer material; and fixing the transferred toner to a paper using heating, pressing processes, etc.

[8] In the above-mentioned electrophotographic method, both of the transfer and development of the image are carried out by the charge of the toner surface, and therefore the toner should necessarily have excellent charging characteristics so as to realize a high-definition image. Therefore, a charge control agent is generally added in the manufacture of toner to improve charging characteristics. Since the charging characteristics depend on the charge density of the toner surface, it is important that the charge control agent is distributed over the toner surface to improve the charging characteristics.

[9] In the case of the conventional black toner, Carbon Black is widely used to realize a black color. Here, the Carbon Black tends to be distributed over the toner surface by a centrifugal force during the toner polymerization since the Carbon Black has a high density. When the Carbon Black is distributed over the toner surface, the charge control agent has a poor charge density due to the conductivity of the Carbon Black, and therefore the charging characteristics of toner may be deteriorated. When the charging characteristics of toner are deteriorated as described above, it is difficult to develop and transfer an image, which leads to the deteriorated printing quality.

[10] Therefore, in order to form a high-definition clear image, it is necessary to manufacture a black toner capable of selectively distributing a charge control agent in the toner surface and minimizing the decrease of charging characteristics due to Carbon Black.

[H]

Disclosure of Invention Technical Problem

[12] The present invention has been made to solve the foregoing problems with the prior art, and therefore an aspect of the present invention is to provide a black polymerized toner having excellent charging characteristics and stability, wherein the black polymerized toner having a core-shell structure is manufactured by adding a polar grafting agent, a hydrophilic polymer and a pigment in the polymerization of a black toner.

[13]

Technical Solution

[14] According to an aspect of the present invention, there is provided a toner having excellent charging characteristics and stability by suppressing the reduction of charge density in a toner surface by the Carbon Black, wherein the black toner is manufactured by adding a polar grafting agent, a hydrophilic polymer and a pigment at predetermined amounts.

[15] As described above, when the toner is manufactured according to the polymerization process, the Carbon Black having a high density tends to be distributed in outer surfaces of toner particles. Therefore, when the Carbon Black is distributed in the toner surface, the charge density of the polymeric charge control agent is reduced by the conductive Carbon Black, which leads to the deteriorated charge density in the toner surface. In order to solve the above problems, a black toner having excellent charging characteristics may be manufactured according to the present invention by adding a polar grafting agent, a hydrophilic polymer and a pigment in the suspension polymerization of toner to suppress the reduction in the surface charge density by the Carbon Black, thereby to maximize the charge density. [16] The final charge in a surface of a toner resin is determined by the chemical structure of the polymeric charge control agent, and its corresponding functional groups are required to determine a negative charge and a positive charge in the chemical structure. For this purpose, a polymeric chain structure containing a functional group is required, and a monomer having a functional group, namely a polar grafting agent, should be used together with a predetermined amount of the polymeric charge control agent to have such a polymer chain structure. The polar grafting agent reacts with the polymeric charge control agent to form a shell of a toner surface, and its charging characteristics are improved with an increasing surface density of the charge control agent.

[17] A hydrophilic polymer having an affinity to a pigment was further added, together with a polar grafting agent, to the black polymerized toner according to the present invention, thus to form a polymer membrane in a shell surface during a polymerization process. Since the pigment has stronger affinity to the hydrophilic polymer than the Carbon Black, the pigment has a higher possibility to be distributed in an outer part of the toner than the Carbon Black during the suspension polymerization. In this case, surfaces of the toner particles are covered with the polar grafting agent, and the polymeric charge control agent and the polymer membrane, which bind to the polar grafting agent, and the pigment having an affinity to the hydrophilic polymer is also present in the surfaces of the toner particles. The Carbon Black is distributed in relatively inner parts of the toner particles since the pigment is distributed in the outer sides of the toner particles. Since the pigment has a lower conductivity than the Carbon Black, it is possible to minimize the reduction of the charge density in the surfaces of the toner particles.

[18] Meanwhile, when the hydrophilic polymer is added according to the present invention, the charging characteristics of toner may be improved, and the polymerization stability may also be improved in the polymerization of toner. Since the hydrophilic polymer has hydrophilicity, the hydrophilic polymer is fixed in an outer part of a polymer formed during an aqueous polymerization process and the hydrophilic polymer functions to easily distribute toner particles formed in an aqueous dispersing agent solution. When the toner particles are distributed thoroughly, the formation of an aggregate body between the toner particles may be prevented, which leads to the improved polymerization stability.

[19] When the polymerization stability is low during the suspension polymerization, polymers are brought together to form an aggregate. When the aggregate is formed, the toner has a low yield, and its production cost is high. Also, since the formed toner particles are irregular in size and shape, the charging characteristics and transfer properties are not maintained at a constant level, which leads to the degraded printing quality. Therefore, the present invention provides a black toner having a high quality by adding a hydrophilic polymer in the polymerization process to solve the above- mentioned problems.

[20] Meanwhile, when at least a predetermined amount of the pigment is added to the black polymerized toner, a black color may become blurred. Therefore, it is important to add the pigment within the range in which the pigment may maximize a charge density without damaging the black color. As a result, the black polymerized toner according to the present invention may be useful to realize a clear black color and maximize the charging characteristics by defining a content of the pigment to a range of 1 to 50 parts by weight, based on 100 parts by weight of the black toner.

[21]

Best Mode for Carrying Out the Invention

[22] Hereinafter, components constituting the black polymerized toner according to the present invention will be described in detail.

[23] The black polymerized toner according to the present invention includes a binder resin monomer constituting toner particles; a charge control agent for improving charging characteristics of toner; a Carbon Black distributed in a binder resin to color a toner; a molecular weight control agent for controlling molecular weight of the toner; a wax for improving a fixing property of toner; a dispersing agent; a polar grafting agent for gelating a surface of toner to form a shell; a hydrophilic polymer for forming a membrane in the toner surface; and a pigment for controlling a position of the Carbon Black.

[24] At least one selected from the group consisting of aromatic vinyl-based, acrylate- based, methacrylate-based, dien-based, acidic olefin-based and basic olefin-based monomers may be used as the binder resin monomer.

[25] At least one selected from the group consisting of styrene, monochlorostyrene, methylstyrene, dimethylstyrene and the like may be used as the aromatic vinyl-based monomer. A content of the aromatic vinyl-based monomer preferably ranges from 30 to 90 % by weight, based on the total weight of the monomer mixture. One reason for defining the content of the aromatic vinyl-based monomer is to adjust a glass transition temperature of toner. In this case, when the content of the aromatic vinyl-based monomer is less than 30 % by weight, an offset phenomenon, in which a toner is attached to a fusing roller in a printing process, may be caused due to the too low glass transition temperature of the toner. On the contrary, when the content of the aromatic vinyl-based monomer exceeds 90 % by weight, the fixing property of toner may be deteriorated due to the too high glass transition temperature of the toner.

[26] The acrylate-based monomer includes methylacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate and the like, the methacrylate-based monomer includes methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dodecyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate and the like, and the dien- based monomer includes butadiene, isoprene and the like. The acrylate-based, methacrylate-based and dien-based monomers may be used alone or in combinations thereof, and contents of the monomers preferably range from 5 to 70 % by weight, based on the total weight of the monomer mixture. A reason for defining the contents of monomers within the above ranges is to adjust a glass transition temperature of toner to a suitable range as in the aromatic vinyl-based monomer.

[27] Meanwhile, the acidic olefin-based monomer includes α,β-ethylene compounds having a carboxyl group, and the like, and the basic olefin-based monomer includes methacrylic ester of aliphatic alcohol having an amine group or a quaternary ammonium, and methacrylamide-based, vinyl amine-based, diaryl amine-based monomers, and ammonium salts thereof. The acidic olefin-based monomer and the basic olefin-based monomer may be used alone or in combinations thereof, and contents of the monomers preferably range from 0.1 to 20 % by weight based on the total weight of the monomer mixture. The acidic olefin-based monomer and the basic olefin-based monomer are added to improve charging characteristics of a toner surface. In this case, when the contents of the monomers exceed 20 % by weight, the reaction stability may be degraded in the polymerization of the toner, which leads to the aggregation between toner particles.

[28] Meanwhile, a hydrophilic monomer is preferably further included in the binder resin monomer according to the present invention, when necessary. The hydrophilic monomer has a strong tendency to be distributed in surfaces of toner particles in characteristics of the suspension polymerization that is carried out in an aqueous phase, and therefore it is helpful to fix Carbon Black in inner parts of the toner particles if the manufactured toner includes a hydrophilic monomer.

[29] The hydrophilic monomer includes acrylic acid, methylmethacrylate, acetate and the like, and they may be used alone or in combinations thereof. A content of the hydrophilic monomer preferably ranges from 0.1 to 20% by weight, based on the total weight of the monomer mixture. When the content of the hydrophilic monomer is less than 0.1 % by weight, it is impossible to effectively distribute a charge control agent and a pigment in a surface of toner, whereas the reaction stability of toner may be degraded during the suspension polymerization that is performed in an aqueous phase when the content of the hydrophilic monomer exceeds 20% by weight.

[30] A cationic charge control agent or an anionic charge control agent may be used as the charge control agent. Here, examples of the cationic polymeric charge control agent include polyester which contain an amine or amide functional group, styrene-acrylic polymer and the like, and the anionic polymeric charge control agent includes an electron acceptor organic complex, chlorinated paraffin, chlorinated polyester, an acid- containing polyester, sulfonyl amine of copper phthalocyanine, a sulfonic acid group- containing styrene acrylic polymer and the like. They may be used alone or in combinations thereof. A content of the charge control agent preferably ranges from 0.01 to 20 % by weight, based on the total weight of the monomer mixture. When the content of the charge control agent is less than 0.01 % by weight, the toner does not have a sufficient charge density that is required for a printing process. On the contrary, when the content of the charge control agent exceeds 20 % by weight, the toner has an excessively high charge density, and therefore an image quality may be rather deteriorated in its printing.

[31] The molecular weight control agent is at least one selected from the group consisting of mercaptan-based compounds such as t-dodecyl mercaptan and n-dodecyl mercaptan, and a content of the molecular weight control agent preferably ranges from 0.1 to 8% by weight, based on the total weight of the monomer mixture. The molecular weight control agent functions to improve a fixing property of toner at a low temperature by lowering a molecular weight of the toner, and therefore the molecular weight control agent may not be added, when necessary. However, when the content of the molecular weight control agent exceeds 8% by weight, an offset phenomenon may be caused due to the too low molecular weight of toner.

[32] The wax, which may be used herein, includes at least one selected from the group consisting of: at least one petroleum refining wax selected from the group consisting of paraffin wax, microcrystalline wax and ceresin wax; a natural wax such as carnauba wax; and at least one synthetic wax selected from the group consisting of polyethylene and polypropylene, and a content of the wax preferably ranges from 0.01 to 30 % by weight, based on the total weight of the monomer mixture. When the content of the wax is less than 0.01 % by weight, a fixing property of toner may be deteriorated in the printing process and the wax may spread into the toner surface, whereas the reaction stability may be problematic when the content of the wax exceeds 30 % by weight.

[33] The dispersing agent is at least one selected from the group consisting of: at least one inorganic dispersing agent selected from the group consisting of calcium phosphate salt, magnesium salt, hydrophilic silica, hydrophobic silica and colloidal silica; at least one non-ionic polymeric dispersing agent selected from the group consisting of poly- oxyethylene alkylether, polyoxyalkylene alkylphenolether, sorbitan fatty acid ester, polyoxyalkylene fatty acid ester, glycerine fatty acid ester, polyvinyl alcohol, alkyl cellulose and polyvinyl pyrrolidone; and at least one ionic polymeric dispersing agent selected from the group consisting of polyacrylamide, polyvinylamine, polyvinylamine N-oxide, polyvinyl ammonium, polydialkyl-diaryl ammonium salt, polyacrylic acid, polystyrene sulfonic acid, polyacrylate, polystyrene sulfonate and polyaminoalkyl acrylate, and a content of the dispersing agent preferably ranges from 0.01 to 10 parts by weight, based on lOOparts by weight of the total dispersion solution. When the content of the dispersing agent is less than 0.01 parts by weight, the reaction stability may be adversely affected during the suspension polymerization. On the contrary, when the content of the dispersing agent exceeds 10 parts by weight, by-products (emulsion particles) are increasingly formed and toner particles are formed with a lower size than a desired toner particle size.

[34] The polar grafting agent includes at least one selected from the group consisting of ethylene dimethacrylate, ethylene glycoldimethacrylate, diethylene glycol diacrylate, 1,6-hexamethylene diacrylate, aryl methacrylate, 1,1,1-trimethylol propane triacrylate and triarylamine, and a content of the polar grafting agent preferably ranges from 0.001 to 10 % by weight, based on the total weight of the monomer mixture. When the content of the polar grafting agent is less than 0.001 % by weight, it is impossible to form a hard shell in a toner surface. On the contrary, when the content of the polar grafting agent exceeds 10% by weight, even the central region of the toner is gelated, which leads to the degraded fixing property of the toner.

[35] Also, the hydrophilic polymer includes polyester-based polymer, styrene acrylic polymer and the like, and they may be used alone or in combinations thereof. A content of the hydrophilic polymer preferably ranges from 0.1 to 20 % by weight, based on the total weight of the monomer mixture. When the content of the hydrophilic polymer is less than 0.1 % by weight, the hydrophilic polymer does not effectively form a polymer membrane on a toner surface. On the contrary, when the content of the hydrophilic polymer exceeds 20% by weight, a phase separation may be caused during the polymerization process, which adversely affects the reaction stability.

[36] Also, the pigment, added in the present invention, includes at least one organic pigment selected from the group consisting of acidic dye-type, basic dye-type, mordant dye-type, diarylide-type, triarylcarbonium-type, quinacridone-type, dioxane-type and oxazine-type pigments, and they may be used alone or in combinations thereof. A content of the pigment preferably ranges from 1 to 50 parts by weight, based on 100 parts by weight of the Carbon Black. When the content of the pigment is less than 1 part by weight, it is impossible to realize a desired charge density to a sufficient extent, whereas the color difference from a black color may be caused when the content of the pigment exceeds 50 parts by weight.

[37] Meanwhile, the black polymerized toner according to the present invention is characterized in that it is manufactured according to the suspension polymerization process. When the toner is manufactured using the suspension polymerization process, the manufacturing process of toner is simple, and it is possible to manufacture spherical toner particles. Hereinafter, the method for manufacturing a toner according to the present invention will be described in more detail.

[38]

[39] (1) Step 1: Preparation of Aqueous Dispersion Solution

[40] An aqueous dispersion solution is prepared by dissolving a dispersing agent in distilled water at a content of 0.01 to 10 parts by weight, based on 100 parts by weight of the aqueous solution. At least one selected from the group consisting of an inorganic dispersing agent and an aqueous organic dispersing agent may be used as the dispersing agent, and an anionic surfactant may be further added, if necessary.

[41] Representative examples of the dispersing agent are the same as described above.

[42] Meanwhile, the anionic surfactant, which may be used herein, includes fatty acid salt, alkyl sulfate ester salt, alkylaryl alkyl sulfate ester salt, dialkyl sulfosuccinate, alkyl phosphate and the like, and a content of the anionic surfactant preferably ranges from 0.001 to 20 parts by weight, based on lOOparts by weight of the total dispersion solution. When the content of the anionic surfactant is less than 0.001 parts by weight, the reaction stability may be adversely affected in the suspension polymerization. On the contrary, when the content of the anionic surfactant exceeds 20 parts by weight, byproducts (emulsion particles) are increasingly formed and toner particles are formed with a lower size than a desired toner particle size.

[43]

[44] (2) Step 2: Preparation of Monomer Mixture

[45] A monomer mixture is prepared as a polymerization material by mixing a binder resin monomer, a hydrophilic monomer, a charge control agent, Carbon Black, a molecular weight control agent, a wax, a dispersing agent, a polar grafting agent, a hydrophilic polymer and a pigment. The specific contents and examples of the materials are the same as described above. That is to say, a monomer mixture is prepared by mixing a binder resin monomer including at least one selected from the group consisting of 30 to 90% by weight of an aromatic vinyl-based monomer, 5 to 70% by weight of at least one acrylate-based monomer, methacrylate-based monomer and dien-based monomer, and 0.1 to 20 % by weight of an acidic or basic olefin-based monomer, based on the total weight of the monomer mixture; 0.1 to 20 % by weight of a hydrophilic monomer or a hydrophilic polymer (based on the total weight of the monomer mixture); 0.1 to 8 % by weight of a molecular weight control agent (based on the total weight of the monomer mixture); 1 to 20 % by weight of Carbon Black (based on the total weight of the monomer mixture); 1 to 50 parts by weight of a pigment (based on lOOparts by weight of the Carbon Black); 0.01 to 30 % by weight of a wax (based on the total weight of the monomer mixture); 0.001 to 10 % by weight of a polar grafting agent (based on the total weight of the monomer mixture); and 0.01 to 25 % by weight of a charge control agent (based on the total weight of the monomer mixture).

[46] A reactant is prepared by adding 0.01 to 5 % by weight of a polymerization initiator to the prepared monomer mixture, base on the total weight of the monomer mixture.

[47] The polymerization initiator, which may be used herein, includes an azo-based initiator such as bisisobutyronitrile, azobisdimethylvaleronitrile and the like; an organic peroxide initiator such as benzoyl peroxide, lauroyl peroxide and the like; and water-soluble initiator such as potassium persulfate, ammonium persulfate and the like, and a content of the polymerization initiator preferably ranges from 0.01 to 5 parts by weight, based on the 100 parts by weight of the monomer mixture. Unreacted materials may be present when the content of the polymerization initiator is less than 0.01 parts by weight, whereas the reaction stability may be degraded due to the very swift response time when the content of the polymerization initiator exceeds 5 parts by weight.

[48]

[49] (3) Step 3: Suspension Polymerization

[50] 1 to 60 parts by weight of the reactant prepared in the Step 2 is added to the aqueous dispersion solution prepared in the Step 1, based on 100 parts by weight the aqueous dispersion solution, and a suspension polymerization process is then carried out by applying a shear force to the aqueous dispersion solution including the monomer mixture.

[51]

[52] (4) Step 4: Separation of Dispersing Agent

[53] When the polymerization process is completed, the prepared toner composition is washed with water and filtered to separate the dispersing agent. This step is repeated until the dispersing agent is completely separated from the toner.

[54]

[55] (5) Step 5: Drying Process

[56] When the dispersing agent is completely separated from the toner, the resulting toner particles are put into a vacuum oven, and dried to obtain the final toner particles.

[57]

[58] The black polymerized toner of the present invention, prepared according to the method, is characterized in that the surface density of the charge control agent is high since the charge control agent is distributed in a shell region, and the black polymerized toner shows excellent charging characteristics since a charge shielding effect by the Carbon Black is minimized by the pigment and the hydrophilic polymer.

[59] Also, the polymerization stability is improved by adding a hydrophilic polymer during the polymerization process, and therefore the formation of aggregate is prevented in this polymerization process. [60]

Mode for the Invention

[61] Hereinafter, exemplary embodiments of the present invention demonstrated that the toner manufactured according to the present invention and a conventional toner are tested for physical properties, and the toner the present invention is excellent in respect to the physical properties, compared to the conventional toner. Therefore, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention

[62]

[63] Example 1

[64] 16 g of polyvinyl alcohol as a dispersing agent, and 2 g of dodecyl benzene sodium ester sulfate as an anionic surfactant were dissolved in 800 g of distilled water in a IL reactor to prepare an aqueous dispersion solution, and the resulting aqueous dispersion solution was heated to a reaction temperature of 7O⁰C.

[65] 180 g of styrene, 40 g of butyl acrylate, 3 g of allylmethacrylate and 2 g of a styrene acrylic polymeric charge control agent having a sulfonic acid group were put into another container, and dissolved thoroughly for 20 minutes while stirring. 9 g of Carbon Black and 1 g of PV-23 (Hostaperm- Violet RL-NF, commercially available from Clariant) were added, and the resulting mixture is stirred in a bead mill at a rotary speed of 1,000 rpm for 1 hour, and beads were removed from the mixture to prepare 160 g of a mixture. The mixture was put into a 7O⁰C water bath, and warmed, and 15 g of a paraffin wax was added thereto, and dissolved thoroughly. 3 g of azobisisobutyr- onitrile as a polymerization initiator was added to the resulting monomer mixture, and stirred for 2 minutes to prepare a reactant.

[66] The reactant was added to the previously prepared aqueous solution, and continuously reacted while stirring at a rotary speed of 10,000 rpm for 20 minutes in a ho- mogenizer. Then, the resulting product was stirred at a rotary speed of 500 rpm for 15 minutes in a conventional stirrer to manufacture a toner.

[67] The toner was washed with water, and filtered to separate the dispersing agent. Then, the washing and filtering processes were repeated until the dispersing agent was removed completely. When the dispersing agent was completely removed from the toner, the resulting toner particles were put into a vacuum oven, and dried to obtain the final toner particles.

[68]

[69] Example 2

[70] 16 g of colloidal silica as a dispersing agent was dissolved in 800 g of distilled water in a IL reactor to prepare an aqueous dispersion solution, and the resulting aqueous dispersion solution was heated to a reaction temperature of 7O⁰C.

[71] 180 g of styrene, 40 g of butyl acrylate, 3 g of allylmethacrylate and 2 g of a styrene acrylic polymeric charge control agent having a sulfonic acid group were put into another container, and dissolved thoroughly for 20 minutes while stirring. 9 g of Carbon Black and 1 g of PV-23 (Hostaperm- Violet RL-NF, commercially available from Clariant) were added thereto, and the resulting mixture is stirred in a bead mill at a rotary speed of 1,000 rpm for 1 hour, and beads were removed from the mixture to prepare 160 g of a mixture. The mixture was put into a 7O⁰C water bath, and warmed, and 15 g of a paraffin wax was added thereto, and dissolved thoroughly. 3 g of azobis- isobutyronitrile as a polymerization initiator was added to the resulting monomer mixture, and stirred for 2 minutes to prepare a reactant.

[72] The reactant was added to the previously prepared aqueous solution, and continuously reacted while stirring at a rotary speed of 10,000 rpm for 20 minutes in a ho- mogenizer. Then, the resulting product was stirred at a rotary speed of 500 rpm for 15 minutes in a conventional stirrer to manufacture a toner.

[73] The toner was washed with water, and filtered to separate the dispersing agent. Then, the washing and filtering processes were repeated until the dispersing agent was removed completely. When the dispersing agent was completely removed from the toner, the resulting toner particles were put into a vacuum oven, and dried to obtain the final toner particles.

[74]

[75] Example 3

[76] 20 g of colloidal silica as a dispersing agent was dissolved in 800 g of distilled water in a IL reactor to prepare an aqueous dispersion solution, and the resulting aqueous dispersion solution was heated to a reaction temperature of 7O⁰C.

[77] 180 g of styrene, 40 g of butyl acrylate, 3 g of allylmethacrylate, 3 g of poly styrene- butadiene-styrene(SBS), 2 g of a styrene acrylic polymeric charge control agent having a sulfonic acid group, and 8 g of polyester were put into another container, and dissolved thoroughly for 20 minutes while stirring. 9 g of Carbon Black and 1 g of PV- 23 (Hostaperm- Violet RL-NF, commercially available from Clariant) were added, and the resulting mixture is stirred in a bead mill at a rotary speed of 1,000 rpm for 1 hour, and beads were removed from the mixture to prepare 160 g of a mixture. The mixture was put into a 7O⁰C water bath, and warmed, and 15 g of a paraffin wax was added thereto, and dissolved thoroughly. 3g of azobisisobutyronitrile as a polymerization initiator was added to the resulting monomer mixture, and stirred for 2 minutes to prepare a reactant.

[78] The reactant was added to the previously prepared aqueous solution, and con- tinuously reacted while stirring at a rotary speed of 10,000 rpm for 20 minutes in a ho- mogenizer. Then, the resulting product was stirred at a rotary speed of 500 rpm for 15 minutes in a conventional stirrer to manufacture a toner.

[79] The toner was washed with water, and filtered to separate the dispersing agent. Then, the washing and filtering processes were repeated until the dispersing agent was removed completely. When the dispersing agent was completely removed from the toner, the resulting toner particles were put into a vacuum oven, and dried to obtain the final toner particles.

[80]

[81] Comparative example 1

[82] A toner was manufactured in the same manner as in Example 1, except that a pigment was not added.

[83]

[84] Comparative example 2

[85] A toner was manufactured in the same manner as in Example 2, except that a pigment was not added.

[86]

[87] Comparative example 3

[88] A toner was manufactured in the same manner as in Example 3, except that a pigment was not added.

[89]

[90] Comparative example 4

[91] A toner was manufactured in the same manner as in Example 3, except that a pigment and a polar grafting agent were not added.

[92]

[93] Experimental example 1 : Measurement of Charge Quantity and Image Density of

Toner

[94] (1) Measurement of Charge Quantity

[95] Each of the toners prepared in the Examples 1 to 3 and the Comparative examples 1 to 3 was mixed with 2% by weight of a surface-treated silica R805 (based on the total weight of the toner), and surface-treated for 3 minutes stirring at a rotary speed of 4,000 rpm in a blender, and the resulting products were measured for charge quantity in an HP4600 printer using a suction method.

[96]

[97] (2) Measurement of Image Density

[98] 100 solid images in which printed papers are filled with a black color were printed, and then the transfer rates of toner were determined by measuring an amount of the toners before/after the printing process, and an amount of undeveloped toner through the weight of a cartridge.

[99] [100] Table 1 [Table 1] [Table ]

[101] *: A polymerization mixture is not filtered. [102] As listed in the Table 1, it was revealed that the toners of the Examples 1, 2 and 3 where the pigment is added during the polymerization have a high charge quantity and an excellent transfer rate, compared to the toners of the Comparative examples. And, it was seen that the toner of the Example 3 wherein the hydrophilic polymer is added has higher transfer rate and charge quantity than the toner of the Example 2. Also, it was revealed that the toner of the Comparative example 4 where the polar grafting agent is not added has lower charge quantity and transfer rate than the toner of the Comparative example 3. As a result, it was seen that the pigment, the hydrophilic polymer and the polar grafting agent contribute together to improving the charging characteristics of the toner.

[103] [104] Experimental example 2: Comparison of Polymerization Stability of Toners [105] In order to compare polymerization stabilities of the toners, the polymerized toner particles were strained with a 100-mesh sieve, and weights of the unstrained and dried aggregates were measured and compared to each other.

[106] Table 2 [Table 2] [Table ]

[107] [108] As listed in the Table 2, it was revealed that, in the case of the toners of the Examples 1 to 3 where the pigment is added during the polymerization of the black toner, the aggregates were formed at a highly smaller amount in the polymerization process, compared to the toners of the Comparative examples. The toner where only the pigment is added has highly improved polymerization stability, but no aggregate is formed at all in the toner of the Example 3 where the hydrophilic polymer is added, therefore it was seen that the polymerization stability of the toner is significantly improved when the pigment and the hydrophilic polymer are added together.

[109]

Industrial Applicability

[HO] The black polymerized toner according to the present invention may be useful to maximize charge density of the charge control agent in the toner surface by adding a polar grafting agent in the manufacture of the black toner, and to improve charging characteristics of the toner by adding a pigment and a hydrophilic polymer to minimize the reduction in the charge density of the toner by the Carbon Black. Also, the hydrophilic polymer functions to improve the polymerization stability by minimizing the formation of the aggregate body due to the aggregation of polymers during the polymerization. The black polymerized toner according to the present invention may be industrially applicable since it is possible to obtain a high yield of a toner having high charging characteristics.

Claims

[1] A black polymerized toner having a core-shell structure, wherein the toner is manufactured in a suspension polymerization method; includes a binder resin monomer, a charge control agent, Carbon Black, a molecular weight control agent, a wax, a dispersing agent, a polar grafting agent, a hydrophilic polymer and a pigment; and a polar grafting agent and a hydrophilic polymer form a polymer membrane in a shell surface.

[2] The black polymerized toner of claim 1, wherein the hydrophilic polymer is at least one polar polymer selected from the group consisting of polyester-based polymer and a styrene acrylic polymer, and a content of the hydrophilic polymer ranges from 0.1 to 20 % by weight, based on the total weight of the monomer mixture.

[3] The black polymerized toner of claim 1, wherein the Carbon Black is present at a content of 1 to 20 % by weight, based on the total weight of the monomer mixture.

[4] The black polymerized toner of claim 1, wherein the pigment is at least one selected from the group consisting of acidic dye-type, basic dye-type, mordant dye-type, diarylide-type, triarylcarbonium-type, quinacridone-type, dioxane-type and oxazine-type pigments, and a content of the pigment ranges from 1 to 50 parts by weight, based on lOOparts by weight of the Carbon Black.

[5] The black polymerized toner of claim 1, wherein the polar grafting agent is at least one selected from the group consisting of ethylene dimethacrylate, ethylene glycoldimethacrylate, diethylene glycol diacrylate, 1,6-hexamethylene diacrylate, allyl methacrylate, 1,1,1-trimethylol propane triacrylate and tri allylamine, and a content of the polar grafting agent ranges from 0.001 to 10 % by weight, based on the total weight of the monomer mixture.

[6] The black polymerized toner of claim 1, wherein the binder resin monomer is at least one selected from the group consisting of aromatic vinyl-based, acrylate- based, methacrylate-based, dien-based, acidic olefin-based and basic olefin- based monomers.

[7] The black polymerized toner of claim 1, wherein the charge control agent is at least one selected from the group consisting of: at least one cationic charge control agent selected from the group consisting of polyester containing amine or amide functional group and a styrene-acrylic polymer: and at least one anionic charge control agent selected from the group consisting of an electron acceptor organic complex, chlorinated paraffin, chlorinated polyester, acid-containing polyester, sulfonyl amine of copper phthalocyanine, a sulfonic acid group- containing styrene acrylic polymer, and a content of the charge control agent ranges from 0.01 to 20 % by weight, based on the total weight of the monomer mixture.

[8] The black polymerized toner of claim 1, wherein the molecular weight control agent is at least one selected from the group consisting of mercaptan-based compounds including t-dodecyl mercaptan and n-dodecyl mercaptan, and a content of the molecular weight control agent ranges from 0.1 to 8% by weight, based on the total weight of the monomer mixture.

[9] The black polymerized toner of claim 1, wherein the wax is at least one selected from the group consisting of: at least one petroleum refining wax selected from the group consisting of paraffin wax, microcrystalline wax and ceresin wax; a natural wax such as carnauba wax; and at least one synthetic wax selected from the group consisting of polyethylene and polypropylene, and a content of the wax ranges from 0.01 to 30 % by weight, based on the total weight of the monomer mixture.

[10] The black polymerized toner of claim 1, wherein the dispersing agent is at least one selected from the group consisting of: at least one inorganic dispersing agent selected from the group consisting of calcium phosphate salt, magnesium salt, hydrophilic silica, hydrophobic silica and colloidal silica; at least one non-ionic polymeric dispersing agent selected from the group consisting of polyoxyethylene alkylether, polyoxyalkylene alkylphenolether, sorbitan fatty acid ester, polyoxyalkylene fatty acid ester, glycerine fatty acid ester, polyvinyl alcohol, alkyl cellulose and polyvinyl pyrrolidone; and at least one ionic polymeric dispersing agent selected from the group consisting of polyacrylamide, polyvinylamine, polyvinylamine N-oxide, polyvinyl ammonium salt, polydialkyl-diaryl ammonium salt, polyacrylic acid, polystyrene sulfonic acid, polyacrylate, polystyrene sulfonate and polyaminoalkyl acrylate, and a content of the dispersing agent ranges from 0.01 to 10 parts by weight, based on 100 parts weight of the total dispersion solution.