JP2008170901A - Electrophotographic toner and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide small particle diameter electrophotographic toner excellent in fluidity, cleaning property and charge stability and having a narrow particle size distribution width, and a method for manufacturing the same. <P>SOLUTION: A melt-kneaded product of a toner composition containing a binder resin having an acid value of 5-30 mgKOH/g and a colorant is emulsified in an aqueous medium containing a water-soluble dispersant having an acid value of ≥200 mgKOH/g to obtain toner particles with irregularity having 100-500 nm average interval between the peaks of protrusions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic toner and a method for producing the same.

  An image forming apparatus that forms an image using an electrophotographic system includes a photoconductor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a fixing unit. The charging unit charges the surface of the photoreceptor. The exposure unit irradiates the charged photosensitive member surface with signal light to form an electrostatic latent image corresponding to the image information. The developing unit supplies toner for electrophotography (hereinafter simply referred to as “toner”) in the developer to the electrostatic latent image formed on the surface of the photoreceptor to form a toner image. The transfer unit transfers the toner image formed on the surface of the photoreceptor to a recording medium. The fixing unit fixes the transferred toner image on the recording medium. The cleaning means is, for example, a cleaning blade, and cleans the surface of the photoconductor by scraping the toner remaining on the surface of the photoconductor after the toner image is transferred with the blade. In such an image forming apparatus, an electrostatic latent image is developed using a one-component developer containing toner or a two-component developer containing toner and a carrier as a developer to form an image. The toner used here is resin particles granulated by dispersing a colorant, a wax as a release agent, etc. in a binder resin as a matrix.

  An image forming apparatus using an electrophotographic system can form an image with good image quality at a high speed and at a low cost. Therefore, the image forming apparatus is used in copying machines, printers, facsimiles, and the like, and has recently been remarkably popular. As a result, the demands on image forming apparatuses have become more severe. In particular, the emphasis is on high definition, high resolution, stable image quality, and high image forming speed of an image formed by the image forming apparatus. In order to achieve these, studies from both the image forming process and the developer are indispensable.

  From the standpoint of developing a high-definition and high-resolution image, it is important to faithfully reproduce the electrostatic latent image from the viewpoint of the developer. Narrowing the width is a problem to be solved. As a method for producing small-diameter toner particles having a narrow particle size distribution width, a polymerization method such as a suspension polymerization method is known. According to the suspension polymerization method, a monomer composition in which a polymerizable monomer and a colorant, and a polymerization initiator, a charge control agent, and other additives used as necessary are uniformly dissolved or dispersed is suspended. The monomer composition particles are formed by being put into an aqueous medium containing a stabilizer and granulated with stirring to form toner particles by polymerization.

  The toner particles obtained by such a suspension polymerization method have a nearly spherical shape and a smooth surface. Therefore, when the toner remaining on the surface of the photoreceptor after the toner image transfer is removed, the toner becomes a cleaning blade. There is a problem that it is difficult to be caught and has poor cleaning properties. In view of such a problem, as a toner having excellent cleaning properties, a toner having irregularities formed on the surface has been proposed (see, for example, Patent Documents 1 and 2).

  In Patent Document 1, a monomer having a radical chain transfer group is graft-polymerized on a toner particle surface formed by emulsion polymerization, suspension polymerization, or dispersion polymerization, or a monomer having two or more radical chain transfer groups is used. A toner produced by graft polymerization and radical polymerization of a monomer having a radical chain transfer group and having irregularities on the particle surface is disclosed.

  In Patent Document 2, the DB value indicating the degree of unevenness of toner particles containing a compound having a melting point of 20 to 120 ° C. is 0.95 or less, and the volume average particle diameter measured by the Coulter method is 6.5 μm or less. An electrostatic charge image developing toner is disclosed. The DB value is a value obtained by dividing the value of the volume average particle diameter by the Coulter method by the value of the volume average particle diameter by the laser diffraction method. The DB value approaches 1 as the shape of the toner particles approaches a true sphere. In Patent Document 2, the three-dimensional unevenness degree of the toner particles is made suitable by setting the DB value in the above range.

  Both the toners disclosed in Patent Documents 1 and 2 have irregularities on the surface, and the toner is easily caught on the cleaning blade during cleaning, so that the cleaning property is improved. However, the toners disclosed in Patent Documents 1 and 2 have a volume average particle size of, for example, a small particle size of 6.5 μm or less, and the toner easily aggregates in the developing container. Occurs. In order to prevent such a decrease in fluidity, an external additive is externally added to the toner particles. However, depending on the surface state of the toner particles, the effect of adding the external additive is not necessarily exhibited. There is. For example, when the surface of the toner particles is smooth, the area of the contact portion between the external additive and the toner particles is small, and the adhesion of the external additive to the toner particles is small, so the external additive is easily detached from the toner particles, The effect of externally adding external additives is hardly exhibited.

  Such a problem may occur even when the toner has irregularities as disclosed in Patent Documents 1 and 2. In the toner disclosed in Patent Document 1, the size and shape of the irregularities formed on the toner cannot be controlled, and the same problem as when the surface of the toner particles is smooth may occur. Further, in the toner disclosed in Patent Document 2, although the degree of unevenness of the toner is defined by the DB value, the degree of unevenness is a value reflecting the shape of the entire toner particle, and the individual protrusions formed on the surface and It does not define the size of the recess. Therefore, the toner disclosed in Patent Document 2 can cause the same problem as when the surface of the toner particles is smooth.

Japanese Patent Laid-Open No. 9-22144 JP 2006-146285 A

  An object of the present invention is to provide a toner for electrophotography having a small particle size which is excellent in fluidity, cleaning property and charging stability and has a narrow particle size distribution width and a method for producing the same.

  The present invention relates to an electrophotographic toner comprising a toner particle containing a binder resin and a colorant and having irregularities having an average interval between convex peaks of 100 nm or more and 500 nm or less, and an external additive. It is.

Further, the invention is characterized in that four or more concave / convex concave portions formed on the toner particles are formed on the toner particle surface on an average per 1 μm ² .

  The present invention is also characterized in that the toner particles have a volume average particle diameter of 3 μm or more and 10 μm or less.

The present invention also provides a method for producing the electrophotographic toner of the present invention,
A melt-kneaded product of a toner composition containing a binder resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less and a colorant is obtained in an aqueous medium containing a water-soluble dispersant having an acid value of 200 mgKOH / g or more. Emulsifying and obtaining toner particles;
And a step of externally adding an external additive to the obtained toner particles.
The present invention is characterized in that the binder resin contains polyester.

  According to the present invention, an electrophotographic toner (hereinafter simply referred to as “toner”) includes toner particles including a binder resin and a colorant and an external additive, and irregularities are formed on the surfaces of the toner particles. . The irregularities on the surface of the toner particles are formed so that the average interval between the peaks of the convex portions is not less than 100 nm and not more than 500 nm. When such irregularities are formed, the contact area between the toner particles and the external additive increases, and the adhesion of the external additive to the toner particles increases. This prevents the external additive from detaching from the toner particles. For example, a small particle size toner produced by a method such as a melt emulsification method for the purpose of reducing the diameter of the toner and narrowing the particle size distribution width. Even in this case, it is possible to prevent the occurrence of problems such as a decrease in fluidity and a decrease in charging stability of the toner having a small particle diameter due to the removal of the external additive. Further, since the detachment of the external additive is prevented, the toner particles and the carrier do not come into direct contact. As a result, it is possible to prevent carrier spent in which components such as a binder resin and a release agent contained in the toner particles adhere to the carrier. Further, since such irregularities are formed on the toner surface, the toner is easily caught on the blade during cleaning, and the toner cleaning property can be improved.

According to the present invention, the concave and convex concave portions formed on the toner particles are formed on the toner particle surface in an average of 4 or more per 1 μm ² . By forming the irregularities in this way, a sufficient amount of an external additive capable of improving the fluidity of the toner can be attached to the toner particles, and the external additive can be prevented from being detached from the toner particles. Therefore, the fluidity of the small particle size toner can be further improved.

  Further, according to the present invention, since the volume average particle diameter of the toner particles is as small as 3 μm or more and 10 μm or less, a high-definition and high-resolution image can be formed. In addition, even in such a small-diameter toner whose fluidity tends to be lowered, the effect of improving fluidity by adding an external additive can be exhibited, and a higher quality image can be formed.

  According to the invention, the toner particles contained in the toner of the invention are a melt-kneaded product of a toner composition containing a binder resin having an acid value of 5 mgKOH / g to 30 mgKOH / g and a colorant. , By emulsifying in an aqueous medium containing a water-soluble dispersant having an acid value of 200 mgKOH / g or more. When a melt-kneaded product of a toner composition containing a binder resin is put into a water-soluble dispersant and granulated, the low molecular weight components of the binder resin on the surface of the granulated melt-kneaded product are eluted in an aqueous medium. The elution site is depressed, and irregularities are formed on the toner surface. Here, a resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less is used as the binder resin, and a dispersant having an acid value of 200 mgKOH / g or more is used as the water-soluble dispersant. The average interval between the peaks of the convex and concave portions can be 0.05 μm or more and 0.5 μm or less, and it is possible to obtain a toner having a small particle size which is excellent in fluidity and cleaning properties and has a narrow particle size distribution width.

  According to the invention, the binder resin includes polyester. Polyester is excellent in transparency, and can impart low temperature fixability, secondary color reproducibility, and the like to the obtained toner particles, and therefore can be particularly suitably used as a binder resin for color toners.

  The electrophotographic toner of the present invention includes a binder resin and a colorant, and includes toner particles in which irregularities having an average interval between convex peaks of 100 nm to 500 nm are formed, and an external additive. To do. According to such a toner, the surface of the toner particle is formed with irregularities having an average interval between the peaks of the convex portions, and the contact area between the toner particles and the external additive is increased. The adhesion force to can be increased. This prevents the external additive from detaching from the toner particles. For example, a small particle size toner produced by a method such as a melt emulsification method for the purpose of reducing the diameter of the toner and narrowing the particle size distribution width. Even in this case, it is possible to prevent the occurrence of problems such as a decrease in fluidity and a decrease in charging stability of the toner having a small particle diameter due to the removal of the external additive. Further, since the detachment of the external additive is prevented, the toner particles and the carrier do not come into direct contact. As a result, it is possible to prevent carrier spent in which components such as a binder resin and a release agent contained in the toner particles adhere to the carrier. Further, the formation of such irregularities on the surface of the toner particles can improve the cleaning property of the toner.

  In the present embodiment, the average interval between the peaks of the convex portions in the toner particles is calculated as follows. For example, the toner particles are photographed at a magnification of 10,000 times with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation). Next, in the photograph of the toner particles, toner particles that are targets for calculating the average interval between the peaks of the convex portions (hereinafter referred to as “calculation targets”) are arbitrarily selected from the photograph. Further, the center of gravity can be determined from the contour portion of the selected toner particle, and the center of gravity of the graphic when the captured image of the toner particle is viewed as a planar graphic is set as the central portion of the toner particle. When the central portion of the toner particles is set, a straight line having a length of 3 μm (3 cm on the photo) passing through the central portion and included in the photographed image of the toner particles to be calculated is drawn on the photographed photograph. Count the number of peaks on the convex part. In the photograph, the peak of the convex part on the toner particle surface appears relatively thin, and the concave part appears dark. For example, when the number of convex peak peaks existing on the straight line is n, the average interval of convex peak peaks in the toner particles is (3000 / n) nm. In this way, the average interval of the peak portions of the convex portions of 100 toner particles extracted at random can be obtained, and the average interval of the peak portions of the convex portions of the entire toner particles contained in the toner can be obtained from the average of these values. it can. The average interval between the peaks of the convex portions may be calculated based on the number of concave portions existing on the straight line.

  If the average interval between the peaks of the convex portions is less than 100 nm, although depending on the particle size of the external additive, the external additive cannot enter the concave and convex portions, and the adhesion strength between the external additive and the toner particles is increased. May not increase. When the average interval between the peaks of the convex portions exceeds 500 nm, the adhesion strength between the external additive and the toner particles is small, and the external additive may be detached from the toner particles as in the case of the toner having no irregularities. More preferably, the average interval between the peaks of the convex portions is not less than 100 nm and not more than 300 nm. When the average distance between the peaks of the convex portions is within such a range, the cleaning property can be further improved, and the detachment of the external additive from the toner particles can be more reliably prevented.

  The depth of the recess is determined by the particle size of the external additive used, and is not particularly limited. However, when the external additive adheres to the recess of the toner particle, at least a part of the external additive is exposed. It is set to be the depth to be. When the depth of the recess is deeper than the depth at which the external additive is exposed, the effect of improving the fluidity of the toner by externally adding the external additive cannot be exhibited. Further, when the toner particles and the carrier are in direct contact with each other, a carrier spent that contaminates the carrier with the toner is generated. The depth of the recess can be set to a suitable depth by the toner manufacturing method of the present invention described later.

The average number of concave and convex concave portions formed on the toner particles is preferably 4 or more, more preferably 4 or more and 100 or less per 1 μm ^{2 on the} toner particle surface. When four or more concave portions are formed on the toner particle surface per 1 μm ^{2 on} average, a sufficient amount of an external additive capable of improving the fluidity of the toner can be adhered to the toner particle, and the toner particles of this external additive Detachment from the toner can be prevented, so that the fluidity of the small particle size toner can be further improved. If the number of recessed portions formed is less than 4 on average per 1 μm ² , the number of formed recessed portions is small and a sufficient amount of external additive cannot be attached to the recessed portion, so that the external additive may be detached. is there. When the average number of concave portions exceeds 100 per 1 μm ^2, the average interval between the peak portions of the convex portions becomes small, and depending on the particle size of the external additive, the external additive cannot enter the concave and convex portions. The adhesion strength between the external additive and the toner particles may not be increased.

  The toner particles preferably have a volume average particle size of 3 μm or more and 10 μm or less. When the volume average particle diameter of the toner particles is 3 μm or more and 10 μm or less, a high-definition and high-resolution image can be formed. Further, even with such a small particle size toner, the fluidity is prevented from being lowered by forming the irregularities as described above, so that a higher quality image can be formed. When the volume average particle diameter of the toner particles is less than 3 μm, the particle diameter of the toner particles becomes too small, and there is a possibility that high charging and low fluidity may occur. When this high charging and fluidity decrease occur, it becomes impossible to stably supply toner to the photoreceptor, and there is a risk that background fogging and image density decrease will occur. When the volume average particle diameter of the toner particles exceeds 10 μm, the toner particles have a large particle diameter, so that a high-definition image cannot be obtained. Further, as the particle size of the toner particles increases, the specific surface area decreases and the charge amount of the toner decreases. When the charge amount of the toner is low, the toner is not stably supplied to the photoconductor, and there is a risk that internal contamination due to toner scattering may occur.

  The toner of the present invention contains a binder resin, a colorant, and other toner additive components. Examples of other toner additive components include a release agent and a charge control agent. The method for producing the toner of the present invention will be described below.

  In the toner production method of the present invention, a melt kneaded product of a toner composition containing a binder resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less and a colorant is dissolved in And a step of emulsifying in an aqueous medium containing an ionic dispersant to obtain toner particles, and a step of externally adding an external additive to the toner particles obtained in the melt emulsification step.

  FIG. 1 is a process diagram showing a procedure of a toner manufacturing method according to an embodiment of the present invention. The toner manufacturing method in the present embodiment includes a melt-kneading process in step s1, an aqueous medium preparing process in step s2, a granulating process in step s3, a cooling process in step s4, and a washing process in step s5. It includes a separation step of step s6, a drying step of step s7, and an external additive addition step of step s8. Any of the melt-kneading process of step s1 and the aqueous medium preparation process of step s2 may be performed first. Further, the cleaning process in step s5 may be performed after the separation process in step s6 as long as it is before the drying process in step s7.

[Melting and kneading process]
In the melt-kneading step of step s1, a toner composition containing a binder resin and a colorant is melt-kneaded and dispersed in a softened binder resin other than the binder resin.

(A) Binder Resin The binder resin is not particularly limited as long as it is commonly used as a binder resin for toner, and examples thereof include polyester, polyurethane, epoxy resin, acrylic resin, and styrene-acrylic resin. . Among these, polyester, acrylic resin, and styrene-acrylic resin are preferable. One of these resins may be used alone, or two or more thereof may be used in combination. Moreover, even if it is the same kind of resin, it is possible to use a plurality of kinds of resins different in any one or more in terms of molecular weight, monomer composition, and the like.

  Polyester is excellent in transparency, excellent in low-temperature fixability and secondary color reproducibility, and therefore suitable as a binder resin for color toners. Known polyesters can be used, and examples thereof include polycondensates of polybasic acids and polyhydric alcohols. As the polybasic acid, those known as polyester monomers can be used, for example, terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid and other aromatic carboxylic acids, maleic anhydride Examples thereof include aliphatic carboxylic acids such as acid, fumaric acid, succinic acid, alkenyl succinic anhydride, and adipic acid, and methyl esterified products of these polybasic acids. A polybasic acid can be used individually by 1 type, or can use 2 or more types together. As the polyhydric alcohol, those known as polyester monomers can be used. For example, aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, hexanediol, neopentylglycol, glycerin, cyclohexanediol, cyclohexanedimethanol And aromatic diols such as alicyclic polyhydric alcohols such as hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, and the like. A polyhydric alcohol can be used individually by 1 type, or can use 2 or more types together. The polycondensation reaction between the polybasic acid and the polyhydric alcohol can be carried out according to a conventional method. For example, the polybasic acid and the polyhydric alcohol are contacted in the presence or absence of an organic solvent and in the presence of a polycondensation catalyst. The process is terminated when the acid value, softening point, etc. of the polyester to be produced reach a predetermined value. Thereby, polyester is obtained. When a methyl esterified product of a polybasic acid is used as a part of the polybasic acid, a demethanol polycondensation reaction is performed. In this polycondensation reaction, for example, the carboxyl group content at the end of the polyester can be adjusted by appropriately changing the mixing ratio of polybasic acid and polyhydric alcohol, the reaction rate, etc., and thus the properties of the resulting polyester are modified. it can. When trimellitic anhydride is used as the polybasic acid, a modified polyester can also be obtained by easily introducing a carboxyl group into the main chain of the polyester. A self-dispersible polyester in water in which a hydrophilic group such as a carboxyl group or a sulfonic acid group is bonded to the main chain and / or side chain of the polyester can also be used. Further, polyester and acrylic resin may be grafted.

  Although it does not restrict | limit especially as an acrylic resin, An acidic group containing acrylic resin can be used preferably. The acidic group-containing acrylic resin is, for example, an acrylic resin monomer or an acrylic resin monomer containing an acidic group or a hydrophilic group and / or a vinyl having an acidic group or a hydrophilic group when an acrylic resin monomer or an acrylic resin monomer and a vinyl monomer are polymerized. It can manufacture by using a system monomer together. Known acrylic resin monomers can be used, for example, acrylic acid that may have a substituent, methacrylic acid that may have a substituent, acrylic ester that may have a substituent, and a substituent. Methacrylic acid ester and the like. Specific examples of the acrylic resin monomer include, for example, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, acrylic Acrylic acid ester monomers such as 2-ethylhexyl acid, n-octyl acrylate, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate Methacrylate monomers such as amyl, methacrylate n-hexyl, methacrylate 2-ethylhexyl, methacrylate n-octyl, decyl methacrylate, dodecyl methacrylate, hydroxyethyl acrylate, hydroxy methacrylate Propyl and the like hydroxyl group (hydroxyl group) containing (meth) acrylic acid ester monomers such as. Acrylic resin monomers can be used alone or in combination of two or more. As the vinyl monomer, known monomers can be used, and examples thereof include styrene, α-methylstyrene, vinyl bromide, vinyl chloride, vinyl acetate, acrylonitrile and methacrylonitrile. A vinyl monomer can be used individually by 1 type, or can use 2 or more types together. The polymerization is carried out by solution polymerization, suspension polymerization, emulsion polymerization or the like using a general radical initiator.

  Examples of the styrene-acrylic resin include styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate. Examples thereof include a copolymer, a styrene-butyl methacrylate copolymer, and a styrene-acrylonitrile copolymer.

  In the present invention, a resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less is used as the binder resin. The acid value is measured according to a potentiometric titration method described in Japanese Industrial Standard (JIS) K0070-1992.

  When the acid value of the binder resin is less than 5 mgKOH / g, the affinity with the water-soluble dispersant is insufficient, and the dispersion stability of the granulated product in water decreases. When the acid value of the binder resin exceeds 30 mgKOH / g, the number of functional groups remaining on the surface of the toner particles increases, so moisture adsorption in a high temperature and high humidity environment (for example, temperature 35 ° C. and humidity 85% RH (Relative Humidity)). The amount increases and the moisture content of the toner may increase. As a result, the volume resistivity of the toner is lowered, and it becomes difficult to perform stable charge amount control against environmental changes even when a charge control agent is added. When the acid value of the binder resin is within the above range, the dispersion stability of the granulated product in water can be maintained, and the toner is excellent in environmental stability with little change in charging performance even when there is environmental fluctuation. Can be manufactured.

  The binder resin has a softening point in consideration of easy granulation operation on the toner particles, kneadability with the additive to the synthetic resin, and more uniform shape and size of the toner particles. Is preferably 150 ° C. or lower, particularly preferably 80 ° C. or higher and 150 ° C. or lower. When the softening point of the binder resin is in such a range, the binder resin can be easily softened in the granulation step of step s3, and granulation can be easily performed. Further, it is easy to disperse the colorant, the release agent and the like in the binder resin in the melt-kneading step of step s1. When the softening point of the binder resin exceeds 150 ° C., it is necessary to increase the melt-kneading temperature in order to soften the binder resin. When a release agent is added as a toner composition, the release temperature is increased due to an increase in the melt-kneading temperature. The mold may be melted too much, making it difficult to disperse the release agent in the binder resin. If the melt kneading temperature is lowered so that the release agent does not melt, the binder resin is not softened, and it may be difficult to disperse the colorant in the binder resin. When the softening point of the binder resin exceeds 150 ° C., the temperature of the mixture of the aqueous medium and the melt-kneaded product needs to be higher than the softening point of the binder resin in the granulation step, and the temperature of the mixture is increased. Therefore, it is necessary to increase the pressure in the container for granulation. If the softening point of the binder resin is less than 80 ° C., the glass transition point (Tg) of the binder resin is likely to be close to room temperature, so that blocking occurs in which the toner thermally aggregates inside the image forming apparatus, The storage stability of the toner is lowered, and there is a risk of inducing printing failure and device failure.

  The glass transition point (Tg) of the binder resin is not particularly limited and can be appropriately selected from a wide range. However, in view of the fixability and storage stability of the obtained toner, it is 50 ° C. or higher and 80 ° C. or lower. Is preferred. When the glass transition point (Tg) of the binder resin is less than 50 ° C., blocking in which the toner thermally aggregates easily occurs in the image forming apparatus, and storage stability may be lowered. When the glass transition point (Tg) of the binder resin exceeds 80 ° C., the fixability of the toner to the recording medium is lowered, and there is a possibility that fixing failure occurs. The weight average molecular weight of the binder resin is preferably 5,000 to 500,000.

(B) Colorant The colorant is not particularly limited, and for example, organic dyes, organic pigments, inorganic dyes, inorganic pigments, and the like can be used.

  Examples of the black colorant include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Examples of yellow colorants include chrome yellow, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, and Benzidine Yellow. GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.

  Examples of the orange colorant include red chrome yellow, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK, C.I. I. Pigment orange 31, C.I. I. And CI Pigment Orange 43.

  Examples of red colorants include bengara, cadmium red, red lead, mercury sulfide, cadmium, permanent red 4R, risor red, pyrazolone red, watching red, calcium salt, lake red C, lake red D, brilliant carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of purple colorants include manganese purple, fast violet B, and methyl violet lake.

  Examples of the blue colorant include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated product, first sky blue, indanthrene blue BC, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. And CI Pigment Blue 60.

  Examples of the green colorant include chrome green, chromium oxide, pigment green B, micalite green lake, final yellow green G, and C.I. I. And CI Pigment Green 7.

  Examples of the white colorant include compounds such as zinc white, titanium oxide, antimony white, and zinc sulfide.

  One colorant can be used alone, or two or more different colorants can be used in combination. Moreover, even if it is the same color, 2 or more types can be used together. The content of the colorant is not particularly limited, but is preferably 0.1 to 20% by weight, more preferably 0.2 to 10% by weight, based on the total amount of the toner composition.

(C) Release agent No particular limitation is imposed on the release agent. For example, paraffin wax and derivatives thereof, petroleum wax such as microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, low Hydrocarbon synthetic waxes such as molecular weight polypropylene wax and derivatives thereof, polyolefin polymer waxes (such as low molecular weight polyethylene wax) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof, candelilla wax and derivatives thereof, wood wax Plant waxes such as beeswax, animal waxes such as beeswax and whale wax, oils and fats synthetic waxes such as fatty acid amides and phenol fatty acid esters, long chain carboxylic acids and derivatives thereof, long chain alcohols and derivatives thereof, silicone polymers Higher fatty acids and the like. Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. Among these, a wax having a melting point equal to or higher than the liquid temperature of the aqueous water-soluble dispersant solution in the granulation step is preferable.

  The melting point of the release agent is preferably 60 ° C. or higher and 130 ° C. or lower. When the melting point of the release agent is less than 60 ° C., the toner particles may aggregate in the image forming apparatus and storage stability may be reduced. If the melting point of the release agent exceeds 130 ° C., the release agent does not melt sufficiently when the toner is heated and fixed, and high temperature offset may occur. When the melting point of the release agent is within the above preferable range, a toner that is excellent in storage stability and can prevent high temperature offset can be obtained. The content of the release agent is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 to 20% by weight based on the total amount of the toner composition.

(D) Charge control agent The charge control agent is not particularly limited, and those for positive charge control and negative charge control can be used. Examples of the charge control agent for controlling positive charge include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, and triphenylmethane. Derivatives, guanidine salts, amidine salts and the like can be mentioned. As charge control agents for controlling negative charges, oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, metal salts of naphthenic acid, salicylic acid and its derivatives, metal complexes and metal salts (metal is Chromium, zinc, zirconium, etc.), fatty acid soaps, long-chain alkyl carboxylates, resin acid soaps, and the like. The charge control agent can be used alone or in combination of two or more as required. The content of the charge control agent is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.5 to 3% by weight based on the total amount of the toner composition.

  In the melt-kneading step, a toner composition containing a binder resin, a colorant and other toner additive components is dry-mixed with a mixer, and then a temperature not lower than the softening point of the binder resin and lower than the thermal decomposition temperature, for example, 80 ° C. The mixture is heated to 200 ° C. or lower, preferably 100 ° C. or higher and 150 ° C. or lower, and melt-kneaded to soften the binder resin and disperse the colorant and toner additive components in the binder resin. Although the toner composition may be melt-kneaded as it is without being dry-mixed, it is better to perform melt-kneading after dry-mixing in the binder resin as a raw material other than the binder resin such as a colorant and a release agent. This is preferable because the dispersibility in the toner can be improved and the characteristics such as charging performance of the obtained toner can be made uniform.

  Known mixers can be used, such as Henschel mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), super mixer (trade name, manufactured by Kawata Co., Ltd.), Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.), etc. Henschel type mixing apparatus, ongmill (trade name, manufactured by Hosokawa Micron Corporation), hybridization system (trade name, manufactured by Nara Machinery Co., Ltd.), Cosmo system (trade name, manufactured by Kawasaki Heavy Industries, Ltd.), and the like.

  A well-known thing can be used also as a kneading machine, for example, common kneading machines, such as a twin-screw extruder, a 3 roll, a laboratory blast mill, can be used. More specifically, for example, TEM-100B (trade name, manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87, PCM-30 (all of which are trade names, manufactured by Ikegai Co., Ltd.), etc. Extruder, Needex (trade name, manufactured by Mitsui Mining Co., Ltd.) and other open roll type kneaders. Among these, an open roll type kneader is preferable.

  Synthetic resin additives such as colorants may be used as a master batch to uniformly disperse the synthetic resin additive in the kneaded product. Two or more additives for synthetic resin may be used as composite particles. The composite particles can be produced, for example, by adding an appropriate amount of water, lower alcohol or the like to two or more additives for synthetic resin, granulating with a general granulator such as a high speed mill, and drying. Masterbatch and composite particles are mixed into the powder mixture during dry mixing.

The softening point of the melt-kneaded product thus obtained is, for example, 80 ° C. or higher and 150 ° C. or lower, and preferably 100 ° C. or higher and 130 ° C. or lower. Further, the melt-kneaded product has a melt viscosity of 10 ⁵ Pa · s or less at a temperature at which the mixture of the melt-kneaded product and the aqueous medium is heated in the granulation step of step s3 described later (hereinafter referred to as “granulation temperature”). It is preferable that This makes it easier to granulate the melt-kneaded product. The softening point of the melt-kneaded product and the melt viscosity at the granulation temperature can be adjusted, for example, by appropriately selecting the constituent materials of the raw materials and the mixing ratio.

[Aqueous medium preparation step]
In the aqueous medium preparation step of step s2, an aqueous medium containing a water-soluble dispersant having an acid value of 200 mgKOH / g or more (hereinafter sometimes simply referred to as “dispersant”) is prepared. The aqueous medium can be prepared, for example, by dissolving or dispersing an appropriate amount of a dispersant described later in water. As water, it is preferable to use water having an electrical conductivity of 20 μS / cm or less. Water whose conductivity is within the above range can be prepared by, for example, an activated carbon method, an ion exchange method, a distillation method, or a reverse osmosis method. Moreover, you may prepare the water whose electrical conductivity is in the said range by combining 2 or more types among these methods. Moreover, it can also prepare using a commercially available pure water manufacturing apparatus, for example, Minipure TW-300RU (trade name) manufactured by Nomura Micro Science Co., Ltd.

  When a dispersant having an acid value of 200 mgKOH / g or more is used, the dispersion stability of the granulated product in an aqueous medium can be maintained. When the acid value of the dispersant is less than 200 mgKOH / g, the affinity between the dispersant and water is insufficient, so the dispersion stability of the granulated product in the aqueous medium is insufficient, and the particle size of the toner particles is controlled. I can't. Although the upper limit of the acid value of the dispersant is not particularly limited, the acid value of a commonly available dispersant is 300 mgKOH / g or less, and within this range, the effect of exhibiting dispersion stability is exhibited. Therefore, the acid value of the dispersant is preferably 200 mgKOH / g or more and 300 mgKOH / g or less.

  As the dispersant, any one commonly used in this field can be used as long as the acid value is in the above range, and examples thereof include water-soluble polymer dispersants. Examples of the water-soluble polymer dispersant include vinyl carboxylic acid homopolymers and copolymers, and salts thereof. Examples of the vinyl carboxylic acid include acrylic acids such as acrylic acid and methacrylic acid, and maleic acid.

  Examples of the homopolymer of vinyl carboxylic acid (hereinafter referred to as “polyvinyl carboxylic acid”) include polyacrylic acids such as polyacrylic acid and polymethacrylic acid. Examples of the salt of polyvinyl carboxylic acid include ammonium salts of polyvinyl carboxylic acid such as ammonium polyacrylate and ammonium polymethacrylate, and alkali metal salts of polyvinyl carboxylic acid such as sodium polyacrylate and sodium polymethacrylate.

  Examples of the copolymer of vinyl carboxylic acid (hereinafter referred to as “vinyl carboxylic acid copolymer”) include a copolymer of vinyl carboxylic acid and a vinyl monomer. Examples of the vinyl carboxylic acid include acrylic acids such as the aforementioned acrylic acid and methacrylic acid, and maleic acid. Examples of the vinyl monomer copolymerized with vinyl carboxylic acid include styrene derivatives such as styrene and α-alkylstyrene such as α-methylstyrene. One vinyl monomer may be used alone, or two or more vinyl monomers may be used in combination.

  Specific examples of the copolymer of vinyl carboxylic acid and vinyl monomer include styrene-acrylic acid copolymer which is a copolymer of styrene and acrylic acid, and copolymer of styrene, α-methylstyrene and acrylic acid. Examples thereof include styrene-acrylic acid copolymers such as styrene-α-methylstyrene-acrylic acid copolymers and styrene-vinylcarboxylic acid copolymers such as styrene-maleic acid copolymers.

  Examples of vinyl carboxylic acid copolymer salts include styrene-acrylic acid copolymer ammonium salts and styrene-acrylic acid copolymer ammonium salts such as styrene-α-methylstyrene-acrylic acid copolymer ammonium salts. Vinyl carboxylic acid copolymer ammonium salts, sodium styrene-acrylic acid copolymer sodium, styrene-acrylic acid copolymer sodium salts such as sodium styrene-α-methylstyrene-acrylic acid copolymer sodium, vinyl Examples include alkali metal salts of carboxylic acid copolymers.

  Polyvinylcarboxylic acid can be produced, for example, by polymerizing vinylcarboxylic acid in the presence of a radical initiator by a solution polymerization method, a suspension polymerization method or an emulsion polymerization method. The vinyl carboxylic acid copolymer is prepared by, for example, subjecting one or more vinyl carboxylic acids and one or more vinyl monomers to a solution polymerization method or suspension in the presence of a radical initiator. It can be produced by polymerizing by a polymerization method or an emulsion polymerization method.

  Among these, polyacrylic acid salts and styrene-acrylic acid copolymer salts are preferred. By using at least one of polyacrylic acid salts and styrene-acrylic acid copolymer salts, the melt-kneaded material can be more uniformly dispersed in the aqueous medium. A toner having a diameter can be obtained more reliably. One type of water-soluble polymer dispersant may be used alone, or two or more types may be used in combination.

  The water-soluble polymer dispersant preferably has a weight average molecular weight (Mw) of 1000 or more and 10,000 or less. By setting the weight average molecular weight (Mw) of the water-soluble polymer dispersant in this range, an increase in the viscosity of the aqueous medium can be suppressed, and the melt-kneaded material can be efficiently dispersed in the aqueous medium. Thereby, for example, small toner particles having a volume average particle diameter of 10 μm or less can be easily generated. Further, since the spread of the particle size distribution width of the toner particles can be suppressed, it is possible to prevent the toner charge amount from becoming non-uniform.

  When the weight average molecular weight (Mw) of the water-soluble polymer dispersant exceeds 10,000, the viscosity of the aqueous medium increases, and it may be difficult to mix with the melt-kneaded product in the granulation step. In addition, the shearing force generated by stirring the mixture in the granulation step is applied to the aqueous medium, making it difficult to apply to the melt-kneaded product. It becomes difficult. As a result, the particle diameter of the toner particles tends to increase, and it may be difficult to produce toner particles having a small particle diameter of 3 μm or more and 10 μm or less. Even if toner particles having a desired average particle diameter can be generated, the particle size distribution width of the toner particles tends to be widened, and the charge amount of the toner may be nonuniform.

  When the weight average molecular weight (Mw) of the water-soluble polymer dispersant is less than 1000, there is a high possibility that an oligomer or an unreacted monomer is contained in the water-soluble polymer dispersant. Since the properties close to those of the oligomer or monomer are exhibited, the function as a dispersant cannot be exhibited in the granulation step, and the melt-kneaded product may not be dispersed in the aqueous medium.

  The weight average molecular weight (Mw) of the water-soluble polymer dispersant can be adjusted by, for example, the type of monomer that is a raw material of the water-soluble polymer dispersant, the degree of polymerization, and the like. When the water-soluble polymer dispersant is made of a copolymer, it can be adjusted by the copolymerization ratio. Here, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the water-soluble polymer dispersant are values in terms of polystyrene measured by Gel Permeation Chromatography (abbreviation: GPC).

  The concentration of the water-soluble polymer dispersant in the aqueous medium is not particularly limited, and it varies from a wide range depending on the types and contents of the binder resin, colorant, release agent and additive contained in the melt-kneaded product. Although it can be appropriately selected, considering the ease of mixing operation of the melt-kneaded product and the aqueous medium, the dispersion stability of the produced toner particles, etc., the total amount of the aqueous medium containing the dispersant at a temperature of 25 ° C. 0.05 wt% or more and 10 wt% or less, more preferably 0.1 wt% or more and 5 wt% or less. When the concentration of the water-soluble polymer dispersant is less than 0.05% by weight, a large amount of an aqueous medium is used in order to realize a suitable use ratio of the water-soluble polymer dispersant to the melt-kneaded product in the granulation step described later. Therefore, the mixing operation of the melt-kneaded product and the aqueous medium may be complicated. When the concentration of the water-soluble polymer dispersant exceeds 10% by weight, the viscosity of the aqueous medium becomes high, which may make it difficult to mix with the melt-kneaded product in the granulation step. In addition, granulation of the melt-kneaded product is hindered, and the melt-kneaded product cannot be uniformly dispersed in the aqueous medium, and the particle size of the toner particles to be produced may be non-uniform.

[Granulation process]
In the granulation step of step s3, a melt-kneaded product of a toner composition containing a binder resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less and a colorant is dissolved in a water-soluble material having an acid value of 200 mgKOH / g or more. The toner particles are obtained by emulsification in an aqueous medium containing a dispersant.

  In the granulation step, the mixture of the aqueous medium and the melt-kneaded product is heated in order to soften the binder resin of the melt-kneaded product obtained by the melt-kneading step in the aqueous medium. The heating temperature (granulation temperature) of the mixture of the aqueous medium and the melt-kneaded product in the granulation step is not particularly limited, and the type and characteristics of the binder resin contained in the melt-kneaded product, such as the softening point, are final. Although it can be appropriately selected from a wide range depending on the particle size of the toner particles to be obtained, it is preferably at a temperature not lower than the softening point of the binder resin contained in the melt-kneaded material and lower than the thermal decomposition temperature, 90 ° C. More preferably, it is 140 degreeC or less. By granulating at such a temperature, the binder resin can be softened without being thermally decomposed, so that granulation can be performed efficiently. In the granulation step, it is not always necessary to heat the mixture of the aqueous medium and the melt-kneaded product. For example, the aqueous medium and the melt-kneaded product are heated to a suitable temperature in advance, and the temperature of the mixture during granulation is the above-mentioned temperature. Heating may not be performed as long as the temperature is maintained.

  Mixing of the aqueous medium and the melt-kneaded material is performed using, for example, an emulsifier or a disperser. As an emulsifier and a disperser (hereinafter, the emulsifier and the disperser are collectively referred to as an emulsifier), an aqueous medium and a melt-kneaded product can be received in a batch type or a continuous type, and a heating unit or a heating unit and An apparatus which has a pressurizing means, mixes an aqueous medium and a melt-kneaded product under heating or heating and pressurization, generates toner particles in the aqueous medium, and discharges the toner particles in a batch type or a continuous type. Is preferred. Moreover, the emulsifier needs to have a stirring means and be capable of mixing the aqueous medium and the melt-kneaded product with stirring. In the emulsifier, it is preferable that the mixing container for mixing the aqueous medium and the melt-kneaded material has a temperature adjusting means. The mixing vessel preferably has pressure resistance, and more preferably has pressure resistance and is provided with a pressure regulating valve. If such a mixing container is used, the temperature of the mixture in the container can be kept almost constant, and the pressure in the mixing container is also kept constant in consideration of the softening point of the binder resin and the vapor pressure of the aqueous medium. Be controlled. In addition, when mixing the aqueous medium and the melt-kneaded product at a heating temperature of 100 ° C. or higher, the emulsifier is equipped with a mechanical seal and the mixing container can be sealed because it is used in a pressurized state. Is preferred.

  Such emulsifiers are commercially available. Examples of commercially available emulsifiers include Ultra Tarrax (trade name, manufactured by IKA Japan Co., Ltd.), Polytron Homogenizer (trade name, manufactured by KINEMATICA), and T.C. K. Batch type emulsifiers such as auto homomixer (trade name, manufactured by Primix Co., Ltd.), Ebara Milder (trade name, manufactured by Ebara Corporation), T. K. Pipeline homomixer, T.W. K. Homomic line flow, T.W. K. Fill mix (all are trade names, manufactured by Primix Co., Ltd.), colloid mill (trade names, manufactured by Shinko Pantech Co., Ltd.), slasher, trigonal wet milling machine (all are trade names, manufactured by Mitsui Miike Chemical Industries, Ltd.) ), Cavitron (trade name, manufactured by Eurotech Co., Ltd.) and continuous flow emulsifiers such as Fine Flow Mill (manufactured by Taiheiyo Kiko Co., Ltd.), Claremix (trade name, manufactured by M Technique Co., Ltd.), Fillmix (product) Name, manufactured by Primix Co., Ltd.).

  The stirring speed of the aqueous medium and the melt-kneaded product is not particularly limited, and the stirring operation can be easily performed according to the kind and content of the binder resin and the colorant in the melt-kneaded product, and the desired particle size. In addition, a value that can obtain toner particles having a particle size distribution and a shape may be appropriately selected. For example, when using an emulsifier equipped with a mixing container, a rotating rotor and a fixed stator provided in the mixing container, the rotational speed of the rotor may be 2000 rpm (2000 rpm) or more and 12000 rpm (12000 rpm) or less. preferable. If the rotational speed of the rotor is less than 2000 rpm, uniform stirring in the mixing vessel is difficult, and the elution of the low molecular components of the binder resin on the surface of the fine particles obtained by granulating the melt-kneaded product may be non-uniform. There is. When the rotational speed of the rotor exceeds 12000 rpm, the load applied to the stirring device increases, which causes a problem in terms of durability of the device.

  The stirring time of the aqueous medium and the melt-kneaded product is not particularly limited, and the types and contents of the binder resin, the colorant, the release agent, the compatibilizing agent and the additive in the melt-kneaded product, the dispersant in the aqueous medium Depending on various conditions such as the type and concentration of the mixture, the heating temperature of the mixture, etc., it can be appropriately selected from a wide range, for example, from 10 minutes to 20 minutes.

  The heating of the mixture is preferably performed while the inside of the mixing container in which the mixture of the aqueous medium and the melt-kneaded material is accommodated is pressurized. Thereby, since the boiling point of the water contained in the mixture can be raised, the mixture can be heated to 100 ° C. or higher without boiling the water in the mixture. Accordingly, it is possible to prevent a decrease in shearing force due to the generation of bubbles, and it is possible to more efficiently granulate the melt-kneaded product.

  When heating the mixture with the inside of the mixing vessel under pressure, the pressure of the gas in the mixing vessel (hereinafter referred to as “pressure in the mixing vessel”) is not particularly limited, and the binder resin in the melt-kneaded product, coloring Mixing operation can be easily carried out according to various conditions such as types and contents of additives, mold release agents, compatibilizers and additives, types and concentrations of dispersants in aqueous media, and heating temperature of the mixture. What is necessary is just to select suitably the pressure from which the toner particle which has the particle size and shape of this is obtained. The pressure in the mixing container is, for example, 0.1 MPa (about 1 atm) or more and 1 MPa (about 10 atm) or less.

  However, if the pressure in the mixing vessel becomes too high, bubbles generated in the mixture may not be lost, but may be refined by pressure and contained in the system, which may hinder granulation of the melt-kneaded product. The pressure in the mixing vessel is preferably a minimum pressure that can suppress boiling of water in the mixture at a desired heating temperature. Therefore, the pressure in the mixing vessel is appropriately selected particularly in consideration of the heating temperature of the mixture. For example, when the heating temperature of the mixture is 150 ° C., the pressure in the mixing container is about 0.5 MPa (about 5 atm).

  As the melt-kneaded product to be mixed with the aqueous medium, a melt-kneaded raw material containing a binder resin, a colorant, a release agent, a compatibilizing agent, an additive, etc. may be used as it is. The obtained solidified product may be used as it is or after being heated again to return to a molten state.

  The mixing ratio of the aqueous medium and the melt-kneaded product is not particularly limited, and is appropriately selected from a wide range according to various conditions such as the content of the binder resin in the melt-kneaded product and the type and content of the dispersant in the aqueous medium. Although it can be selected, when a water-soluble polymer dispersant is used as a dispersant from the viewpoint of efficiently performing a mixing operation of an aqueous medium and a melt-kneaded product, a separation operation of toner particles from the aqueous medium, etc., the kneaded product 100 The aqueous medium is preferably used in an amount of 100 parts by weight to 500 parts by weight with respect to parts by weight.

  By heating and stirring the mixture of the aqueous medium and the melt-kneaded material as described above, toner particles containing the binder resin and the colorant are generated in the aqueous medium. The toner particles thus produced have a small particle size and a narrow particle size distribution range. In addition, when a melt-kneaded product of a toner composition containing a binder resin is put into a water-soluble dispersant and granulated, the low molecular weight component of the binder resin on the surface of the granulated melt-kneaded product is eluted in an aqueous medium. As a result, the elution site is depressed and irregularities are formed on the toner surface.

  The acid value of the binder resin is an index representing the amount of carboxyl groups per unit weight. The higher the value, the more carboxyl groups present in the resin per unit weight and the lower the molecular weight of the resin. Moreover, when there are many carboxyl groups present in the resin per unit weight, it is easy to disperse in an aqueous medium containing a dispersant and to be easily eluted. Also, the acid value of the dispersant, like the binder resin, has a lower molecular weight as the value is higher. When the same weight is used, the lower the molecular weight, the higher the molar ratio of the dispersant contained in the aqueous medium, the better the resin dispersibility, and the higher the resin elution capacity.

  Here, a melt-kneaded material granulated by using a resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less as a binder resin and using a dispersant having an acid value of 200 mgKOH / g or more as a water-soluble dispersant. The elution amount of the binder resin on the surface is suitable. As a result, irregularities are formed on the surface of the toner particles, and the average interval between the convex peaks of the irregularities can be 0.05 μm or more and 0.5 μm or less. The toner having such irregularities is excellent in fluidity and cleaning properties. Further, a toner having a small particle size with a narrow particle size distribution range can be obtained by granulating a melt-kneaded product of a toner composition containing a binder resin into an aqueous medium containing a water-soluble dispersant.

[Cooling process]
In the cooling step of step s4, the mixture containing the granulated toner particles (hereinafter referred to as “aqueous slurry”) is cooled. The cooling of the aqueous slurry may be performed by forced cooling in which heating is stopped after the toner particles are generated in the granulation process in step s3 and forcibly cooled using a refrigerant, or natural cooling in which the toner is allowed to cool as it is. preferable.

  In the cooling step, the toner particles are uniformly dispersed in the aqueous medium and can be cooled while maintaining the shape and size. For example, the volume average particle diameter is 10 μm or less, preferably 3 μm or more and 10 μm or less. Toner particles having a small particle size distribution width and a uniform particle size can be obtained. The mixture is preferably cooled with stirring. When the mixture is cooled without stirring, the dispersion stabilizing effect by the water-soluble polymer dispersant is not sufficiently exhibited, and the toner particles may be fused to each other.

  Moreover, when granulation of the resin kneaded material is performed under pressure with the heating temperature of the mixture being 100 ° C. or higher, it is preferable to continue the pressure in the cooling step. When the temperature of the mixture is 100 ° C. or higher, if the pressure is stopped and the pressure in the mixing container is returned to atmospheric pressure, the water in the mixture boils and many bubbles are generated, making subsequent processing difficult. become. The pressure in the mixing container is preferably returned to atmospheric pressure when the temperature of the mixture in the mixing container becomes 50 ° C. or lower. After the mixture in the mixing container is cooled to room temperature (about 25 ° C.), the pressure in the mixing container is increased to atmospheric pressure. More preferably, it is returned.

[Washing process]
In the washing process of step s5, the toner particles contained in the cooled aqueous medium are washed. The toner particles are washed to remove impurities derived from the dispersant and the dispersant. If the dispersant and the impurities remain in the toner particles, the charging performance of the obtained toner particles may become unstable. Moreover, there exists a possibility that charging property may fall under the influence of the water | moisture content in air.

  The toner particles can be washed, for example, by adding water to the mixture, stirring and washing. The toner particles are washed with water repeatedly using a conductivity meter until the conductivity of the supernatant liquid separated from the mixture by centrifugation or the like becomes 100 μS / cm or less, preferably 10 μS / cm or less. As a result, it is possible to more reliably prevent the dispersant and impurities from remaining and to make the charging performance of the toner particles more uniform.

  The water used for washing is preferably water having a conductivity of 20 μS / cm or less. Such water can be prepared, for example, by an activated carbon method, an ion exchange method, a distillation method, a reverse osmosis method, or the like. Moreover, you may prepare water combining 2 or more types among these methods. The toner particles may be washed with water either batchwise or continuously. The temperature of the washing water is not particularly limited, but is preferably 10 ° C or higher and 80 ° C or lower.

[Separation process]
In the separation step of step s6, the toner particles are separated and collected from the mixture containing the washed toner particles. Separation of the toner particles from the aqueous medium can be performed, for example, by filtration, suction filtration, centrifugation, or the like.

  When the washing process of step s5 is performed after the separation process of step s6, for example, the toner particles can be washed by washing the separated toner particles with water. The toner particles are washed with water using an electric conductivity meter or the like until the conductivity of the washing water after washing the toner particles becomes 100 μS / cm or less, preferably 10 μS / cm or less. As a result, it is possible to reliably prevent the dispersing agent and impurities from remaining, and to make the charging performance of the toner particles more uniform.

[Drying process]
In the drying step of step s7, the washed toner particles are dried. The toner particles, which are toner particles, can be dried by a freeze drying method, an airflow drying method, or the like. When the toner particles are dried in step s7, the production of the toner particles is finished.

[External additive addition process]
In the external additive addition step of step s8, an external additive is externally added to the obtained toner particles. Examples of the external additive include inorganic fine powders such as silica fine powder, titanium oxide fine powder, and alumina fine powder. These inorganic fine powders are used for the purpose of hydrophobization, chargeability control, etc. Silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane coupling agents, silane coupling agents having functional groups, and other organic It is preferably treated with a treating agent such as a silicon compound. Two or more treatment agents may be used in combination. Such external additives can be used alone or in combination of two or more. The amount of the external additive added is 2 weights with respect to 100 parts by weight of the toner particles in consideration of the charge amount necessary for the toner, the influence on the abrasion of the photoreceptor due to the addition of the external additive, and the environmental characteristics of the toner. Part or less is preferred.

  The external additive preferably has a number average particle size of primary particles of 10 to 500 nm. By using an external additive having such a particle size, the effect of improving the fluidity of the toner is more easily exhibited. In addition, by using the external additive having such a particle size, the effect of preventing the external additive from detaching due to the formation of irregularities having an average interval between the convex peaks of 100 nm or more and 500 nm or less is exhibited. The effect of improving the fluidity of the toner and preventing the spent of the carrier can be achieved.

  Thus, the toner in which the external additive is externally added to the toner particles can be used as it is as a one-component developer, or can be mixed with a carrier and used as a two-component developer. When used as a two-component developer, magnetic particles can be used as the carrier. Specific examples of the particles having magnetism include metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum or lead. Among these, ferrite is preferable.

  Further, a resin-coated carrier in which magnetic particles are coated with a resin, or a resin-dispersed carrier in which magnetic particles are dispersed in a resin may be used as the carrier. The resin for coating the magnetic particles is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene / acrylic resins, silicone resins, ester resins, and fluorine-containing polymer resins. . Moreover, although it does not restrict | limit especially as resin used for a resin dispersion type carrier, For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, etc. are mentioned.

The shape of the carrier is preferably a spherical shape or a flat shape. The particle size of the carrier is not particularly limited, but is preferably 30 to 50 μm in consideration of high image quality. Furthermore, the resistivity of the carrier is preferably 10 ⁸ Ω · cm or more, more preferably 10 ¹² Ω · cm or more. The carrier resistivity is determined by placing the carrier in a container having a cross-sectional area of 0.50 cm ² and tapping it, then applying a load of 1 kg / cm ² to the particles packed in the container and placing the load between the load and the bottom electrode. This is a value obtained by reading a current value when a voltage generating an electric field of 1000 V / cm is applied. When the resistivity is low, when a bias voltage is applied to the developing sleeve, charges are injected into the carrier, and carrier particles easily adhere to the photoreceptor. Further, breakdown of the bias voltage is likely to occur.

  The magnetization strength (maximum magnetization) of the carrier is preferably 10 to 60 emu / g, more preferably 15 to 40 emu / g. The magnetization strength depends on the magnetic flux density of the developing roller, but under the general magnetic flux density conditions of the developing roller, if it is less than 10 emu / g, the magnetic binding force does not work and causes carrier scattering. There is a fear. On the other hand, if the magnetization strength exceeds 60 emu / g, it is difficult to maintain a non-contact state with the image carrier in the non-contact development in which the carrier spikes are too high. Further, in the contact development, there is a risk that a sweep is likely to appear in the toner image.

The usage ratio of the toner and carrier in the two-component developer is not particularly limited and can be appropriately selected according to the type of toner and carrier. However, if a resin-coated carrier (density 5 to 8 g / cm ² ) is taken as an example, development The toner may be used so that the toner is contained in 2 to 30% by weight, preferably 2 to 20% by weight of the total amount of the developer. In the two-component developer, the carrier coverage with the toner is preferably 40 to 80%.

(Example)
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified.

[Preparation of water]
In the following Examples and Comparative Examples, water having an electrical conductivity of 0.5 μS / cm was used as water for preparing an aqueous medium and water for cleaning toner particles. This washing water was prepared from tap water using an ultrapure water production apparatus (trade name: Minipure TW-300RU, manufactured by Nomura Micro Science Co., Ltd.). The electrical conductivity of water was measured using Lacom Tester EC-PHCON10 (trade name, manufactured by ASONE Corporation).

[Average distance between convex peaks]
The toner particles were photographed at a magnification of 10,000 times with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation), and the central portion of the toner particles to be calculated was set in the photograph of the toner particles. Next, on this photograph, a straight line having a length of 3 μm (3 cm on the photograph) passing through the center and included in the photographed image of the toner particles to be calculated is drawn, and the number of convex peaks on the straight line is calculated. I counted. From the result of counting the number of convex peaks, the average interval of convex peaks is obtained for 100 toner particles extracted at random, and from the average of these values, the total convexity of the toner particles contained in the toner of the embodiment is calculated. The average interval between the summits was obtained.

[Volume average particle size]
20 ml of a sample and 1 ml of sodium alkyl ether sulfate are added to 50 ml of an electrolytic solution (trade name: ISOTON-II, manufactured by Beckman Coulter, Inc.), and ultrasonic waves are applied using an ultrasonic disperser (trade name: UH-50, manufactured by STM). A sample for measurement was prepared by dispersion treatment at a frequency of 20 kHz for 3 minutes. This sample for measurement was measured using a particle size distribution measuring device (trade name: Multisizer 3, manufactured by Beckman Coulter, Inc.) under the conditions of aperture diameter: 100 μm, number of measured particles: 50000 count, and volume particle size distribution of sample particles. From this, the volume average particle size was determined.

[Weight average molecular weight and number average molecular weight of binder resin and water-soluble dispersant]
The weight average molecular weight Mw and the number average molecular weight Mn of the binder resin and the dispersant were measured as follows. A column set at a temperature of 40 ° C. was used in a GPC apparatus (trade name: HLC-8220 GPC, manufactured by Tosoh Corporation), and the injection amount of the sample solution was measured as 100 mL. As the sample solution, a solution obtained by drying a 0.25 wt% (solid content concentration) tetrahydrofuran solution of a sample obtained by drying the binder resin or the water-soluble polymer dispersant overnight was used. The molecular weight calibration curve was prepared using standard polystyrene (monodisperse polystyrene).

[Glass transition point of binder resin (Tg)]
The glass transition point (Tg) of the binder resin was measured as follows. Using a differential scanning calorimeter (trade name: DSC220, manufactured by Seiko Denshi Kogyo Co., Ltd.), a DSC curve is measured by heating 1 g of a sample at a heating rate of 10 ° C. per minute in accordance with Japanese Industrial Standard (JIS) K7121-1987. did. Draw the endothermic peak corresponding to the glass transition of the obtained DSC curve at a point where the slope is maximum with respect to the straight line that extends the base line on the high temperature side to the low temperature side and the curve from the rising part of the peak to the vertex. The temperature at the intersection with the tangent was determined as the glass transition point (Tg).

[Number average particle diameter of primary particles of external additive]
Each of 100 particles randomly taken out from the external additive was observed at a magnification of 20000 by observation with a transmission electron microscope, and the particle size of the primary particles was measured by image analysis. The number average particle size was calculated from the obtained measured values.

[Acid value]
The measurement was performed in accordance with a potentiometric titration method described in Japanese Industrial Standard (JIS) K0070-1992.

  Moreover, polyester resin AE shown in Table 1 was used as binder resin. Similarly, styrene-acrylic acid copolymers a to c shown in Table 2 were used as dispersants.

(Example 1)
88 parts of polyester resin A as a binder resin, 5 parts of colorant (trade name: KET.BLUE111, manufactured by Dainippon Ink Co., Ltd.), release agent (trade name: HNP-10, manufactured by Nippon Seiwa Co., Ltd.) 5 parts and 2 parts of a charge control agent (trade name: Copy Charge N4P VP 2481, manufactured by Clariant Japan KK) were mixed and dispersed in a Henschel mixer for 3 minutes to obtain a toner raw material. The obtained toner raw material was melt kneaded and dispersed using a twin screw extruder (trade name: PCM-30, manufactured by Ikegai Co., Ltd.) to prepare a resin kneaded product of the toner composition. The operating conditions of the twin screw extruder were a cylinder set temperature of 110 ° C., a barrel rotation speed of 300 revolutions per minute (300 rpm), and a raw material supply speed of 20 kg / hour.

  As a dispersant, 100 parts (solid content) of styrene-acrylic acid copolymer a was used and mixed with 900 parts of water to prepare an aqueous medium having a dispersant concentration of 10% by weight.

  In a metal mixing vessel equipped with a pressure regulating valve, heating means and rotor-stator stirring means (diameter 30 mm), 100 parts of the resin kneaded material prepared as described above and 550 parts of an aqueous medium (dispersant concentration 10% by weight). The mixture was stirred and mixed for 10 minutes with a rotor-stator stirring means while heating so that the temperature of the mixture in the mixing container became 120 ° C. under a pressure of 5 atm (5 atm), thereby generating toner particles. At this time, the rotational speed of the rotor in the rotor-stator stirring means was set to 8000 rpm.

  After producing the toner particles as described above, heating was stopped, and the mixture containing the produced toner particles was cooled to 20 ° C. while stirring the mixture. At this time, the rotational speed of the rotor in the rotor stator type stirring means was set to 8000 rpm per minute.

  Next, water having a conductivity of 0.5 μS / cm (temperature of 20 ° C.) was added to the mixture to clean the toner particles. To clean the toner particles, water (conductivity 0.5 μS / cm) is added to the mixture, and the solid content is adjusted to 10% by adding water, and then the stirring blade is rotated using a turbine type stirring blade. It was performed by stirring for 30 minutes at a speed of 300 revolutions per minute (300 rpm). This washing operation was repeated until the electrical conductivity of the supernatant liquid separated from the stirred mixture by centrifugation was 10 μS / cm or less.

  The solid content containing toner particles was separated from the washed mixture by centrifugation. The collected solid content was lyophilized to obtain toner particles. The obtained toner particles had a volume average particle size of 7.2 μm and an average interval between the peak portions of the convex portions of 273 nm.

  To 100 parts of the obtained toner particles, 2 parts of silica (manufactured by Nippon Aerosil Co., Ltd.) having a primary particle number average particle diameter of 12 nm and silica having a primary particle number average particle diameter of 80 nm (Taika Corporation). The toner of Example 1 was obtained by externally adding 0.5 part.

(Example 2)
A toner of Example 2 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin B. The volume average particle diameter of the toner particles contained in the toner of Example 2 is 5.0 μm, and the average interval between the convex peaks is 123 nm.

(Example 3)
A toner of Example 3 was obtained in the same manner as in Example 1 except that the binder resin was changed to the polyester resin C. The volume average particle diameter of the toner particles contained in the toner of Example 3 is 3.9 μm, and the average interval between the convex peaks is 109 nm.

Example 4
A toner of Example 4 was obtained in the same manner as in Example 1, except that the dispersant was changed to styrene-acrylic acid copolymer b. The volume average particle diameter of the toner particles contained in the toner of Example 4 is 9.1 μm, and the average interval between the convex peaks is 375 nm.

(Example 5)
A toner of Example 5 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin B and the dispersant was changed to styrene-acrylic acid copolymer b. The volume average particle size of the toner particles contained in the toner of Example 5 is 6.5 μm, and the average interval between the convex peaks is 231 nm.

(Example 6)
A toner of Example 6 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin C and the dispersant was changed to styrene-acrylic acid copolymer b. The volume average particle diameter of the toner particles contained in the toner of Example 6 is 5.5 μm, and the average interval between the convex peaks is 176 nm.

(Comparative Example 1)
A toner of Comparative Example 1 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin D and the dispersant was changed to styrene-acrylic acid copolymer c. The volume average particle diameter of the toner particles contained in the toner of Comparative Example 1 is 185.0 μm, and the unevenness where the distance between the peaks of the protrusions is 100 nm or more and 500 nm or less was not formed on the surface of the toner particles. The toner of Comparative Example 1 was not evaluated because the volume average particle size of the toner particles was too large.

(Comparative Example 2)
A toner of Comparative Example 2 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin B and the dispersant was changed to styrene-acrylic acid copolymer c. The volume average particle diameter of the toner particles contained in the toner of Comparative Example 2 is 97.8 μm, and the unevenness where the distance between the peaks of the protrusions is 100 nm or more and 500 nm or less was not formed on the surface of the toner particles. The toner of Comparative Example 2 was not evaluated because the volume average particle size of the toner particles was too large.

(Comparative Example 3)
A toner of Comparative Example 3 was obtained in the same manner as in Example 1 except that the binder resin was changed to polyester resin E and the dispersant was changed to styrene-acrylic acid copolymer c. The volume average particle diameter of the toner particles contained in the toner of Comparative Example 3 is 42.8 μm, and the unevenness where the distance between the peak portions of the protrusions is 100 nm or more and 500 nm or less was not formed on the toner particle surface. The toner of Comparative Example 3 was not evaluated because the volume average particle size of the toner particles was too large.

(Comparative Example 4)
The toner of Comparative Example 4 was obtained in the same manner as in Example 1 except that the binder resin was changed to a styrene acrylic resin (glass transition temperature 62 ° C., weight average molecular weight 32000, Mw / Mn = 2.7). It was. The volume average particle diameter of the toner particles contained in the toner of Comparative Example 4 is 7.2 μm.

  Using the toners of Examples and Comparative Examples, the average number of recesses, transparency, adhesion strength of external additives, occurrence of spent on carriers, and cleaning properties were evaluated as follows. However, the average number of recesses, the adhesion strength of external additives, the occurrence of carrier spent, and the cleaning property were evaluated only for the toners of the examples.

[Average number of recesses]
The toner particles were photographed at a magnification of 10,000 times with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation), and the central portion of the toner particles to be calculated was set in the photograph of the toner particles. Next, a square of 1 μm ² was drawn at the center of the photograph, and the number of recesses existing in the range was counted. The number of concave portions was determined for 100 toner particles extracted at random, and the average number of concave portions of the entire toner particles contained in the toner of the example was obtained. The case where the average number of recesses was 4 or more per 1 μm ^{2 of} the toner particle surface was evaluated as ◯, and the case where it was 3 or less was evaluated as x.

[transparency]
The toner of the example and a carrier in which 0.5 part of a styrene-fluoroalkyl copolymer is coated on 100 parts of ferrite on a ferrite having a volume average particle diameter of 50 μm, and the toner concentration is 5 of the total amount of the two-component developer. The two-component developer containing the toner of the example was manufactured.

This two-component developer was filled in a copying machine (trade name: MX-4500FN, manufactured by Sharp Corporation), and an image sample was prepared so that the toner adhesion amount was 1.7 mg / cm ² on the OHP sheet. About this image sample, the HAZE value was measured using the turbidimeter (made by Nippon Denshoku Industries Co., Ltd.), and it was set as the transparency parameter | index. The smaller the HAZE value, the better the transparency.
A: Extremely high transparency. 15 or less.
○: Good. 20 or less.
X: Lack of practicality as a color toner. 25 or more

[Adhesive strength of external additives]
A 0.2 wt% triton aqueous solution (polyoxyethyl phenyl ether) was added to 2.0 g of the toner weighed in a 50 mL beaker, and gently stirred with a spatula to fully wet the toner with the aqueous solution. The toner and the aqueous solution were treated with an ultrasonic homogenizer (trade name US-300T, manufactured by Nippon Seiki Seisakusho Co., Ltd.) at an output of 40 μA for 4 minutes to desorb external additives from the toner particles. At this time, the beaker was immersed in ice water so that the toner and the aqueous solution in the beaker were 40 ° C. or lower. After the treatment, the mixture was allowed to stand for 3 hours to allow the toner to settle. Then, the supernatant was discarded, 50 mL of pure water was added, and the mixture was blended with a spatula and stirred with a stirrer for 5 minutes. After stirring, suction filtration was performed using a membrane filter having a diameter of 1 μm, the toner was returned to the beaker, 50 mL of pure water was added again, and stirring and suction filtration were performed with a stirrer for 5 minutes. After sufficiently filtering, it is dried overnight in a constant temperature bath at 40 ° C., the fluorescence intensity of the characteristic element derived from the external additive is measured by fluorescent X-ray measurement, and the following formula is used from the amount of change before and after the ultrasonic treatment. The adhesion strength of the external additive was calculated.
Adhesion strength = (fluorescence intensity after treatment) / (trend strength before treatment) × 100 (%)

The evaluation criteria for the adhesion strength of the external additive are shown below.
A: Very good. Adhesion strength is 70% or more.
○: Good. Adhesion strength is 65% or more and less than 70%.
Δ: No problem in actual use. Adhesion strength is 60% or more and less than 65%.
×: Unusable. Adhesive strength is less than 60%.

[Career spent]
The same two-component developer as described above was stirred for 30 minutes with VIBRATING MIXER MILL (manufactured by Mitamura Riken Kogyo Co., Ltd.), and then the carrier surface was washed with an aqueous surfactant solution, and a solid carbon analyzer (trade name: EMIA-110). , Manufactured by HORIBA, Ltd.), the carbon increase rate on the carrier surface was measured. The greater the rate of carbon increase, the greater the degree of carrier contamination with toner. The evaluation criteria for career spent are shown below.
A: Very good. Carbon increase rate is less than 0.05%.
○: Good. Carbon increase rate is 0.05% or more and less than 0.10%.
Δ: No problem in actual use. Carbon increase rate is 0.10% or more and less than 0.15%.
×: Unusable. Carbon increase rate is 0.15% or more.

[Cleanability]
A two-component developer similar to that described above was filled in a copying machine (trade name: MX-4500FN, manufactured by Sharp Corporation), and 10,000 sheets of a chart with a printing rate of 5% were continuously printed on A4 size recording paper. . Thereafter, it was visually confirmed whether filming had occurred on the surface of the photoreceptor. When filming did not occur, the cleaning property was evaluated as good (◯). When filming occurred, the cleaning property was evaluated as poor (x).

  In the toners of Examples and Comparative Examples, the acid value of the binder resin, the acid value of the dispersant, the volume average particle diameter of the toner particles, the transparency, and the average distance between the convex peaks and the average number of concave parts in the toners of the examples. Table 3 shows the results of evaluation of the adhesion strength of the additive, the occurrence of the spent of the carrier, and the cleaning property.

  From Table 3, it can be seen that the toner of the present invention is excellent in fluidity and cleaning properties and has a small particle size.

FIG. 6 is a process diagram illustrating a procedure of a toner manufacturing method according to an embodiment of the present invention.

Claims (5)

A toner particle comprising a binder resin and a colorant, wherein the irregularities having an average interval between the peaks of the protrusions of 100 nm to 500 nm are formed;
An electrophotographic toner comprising an external additive. 2. The toner for electrophotography according to claim 1, wherein an average of four or more concave and convex concave portions formed on the toner particles is formed on the toner particle surface per 1 [mu] m < ² >.   The toner for electrophotography according to claim 1, wherein the toner particles have a volume average particle diameter of 3 μm or more and 10 μm or less. A method for producing an electrophotographic toner according to any one of claims 1 to 3,
A melt-kneaded product of a toner composition containing a binder resin having an acid value of 5 mgKOH / g or more and 30 mgKOH / g or less and a colorant is obtained in an aqueous medium containing a water-soluble dispersant having an acid value of 200 mgKOH / g or more. Emulsifying and obtaining toner particles;
And a step of externally adding an external additive to the obtained toner particles.   The method for producing an electrophotographic toner according to claim 4, wherein the binder resin contains polyester.

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