JP6244858B2 - Method for producing pulverized toner for developing electrostatic latent image - Google Patents

Description

  The present invention relates to a pulverized toner for developing an electrostatic latent image for developing an electrostatic latent image formed in electrophotography.

  Conventionally, it has been proposed to use crystalline polyester as a magnetic toner for the purpose of improving toner fixing performance (see, for example, Patent Documents 1 and 2).

  However, when crystalline polyester is used for the magnetic toner, the resistance of the binder resin of the toner is lowered due to the crystalline structure of the crystalline polyester, and the charging performance of the toner is lowered. Further, it becomes a leakage point through the magnetic powder, and further, the charging performance of the toner is lowered, and there is a problem in the charging stability performance particularly in a high temperature environment. Further, since crystalline polyester has a relatively high adhesive force, if crystalline polyester is present on the toner surface, the adhesion of toner particles is greatly increased and the fluidity of the toner is greatly decreased. If the fluidity is poor, the toner transportability deteriorates, resulting in a decrease in developability and a replenishment failure. There has been a demand for maintaining good fluidity while maintaining good fixability and obtaining good image quality.

  In order to improve the development stability, it is necessary to stabilize the charging of the toner particles. In a magnetic toner, a magnetic substance may be present near the toner surface or may protrude from the toner surface as a convex portion, which causes a problem that the charge amount of the toner decreases as a charge leakage point. .

  In order to solve these problems, a technology has been proposed in which the surface distribution state of the magnetic material of the magnetic toner is limited to improve charging stability and image stability (for example, patents). References 3 and 4). These techniques can keep the distance between the magnetic material in the vicinity of the toner surface and the toner surface constant, thereby reducing the charge leak point and certainly suppressing the decrease in the toner charge amount.

  However, when a material having a low melting point among toner materials, such as wax, is present in the portion where the constant distance is maintained, the adhesive force may suddenly increase starting from this material. For this reason, the adhesion force between the toners is increased, and the toners are aggregated to cause deterioration in toner storage stability and inconvenience to other processes.

JP 2011-150205 A JP 2006-078983 A JP 2002-072540 A JP 2002-072546 A

  The present invention is less influenced by the environment, has a stable charging performance especially under high temperature and high humidity, has no fog, has a high image density even in long-time use, has excellent fixability and image reproducibility, and fluidity An object of the present invention is to provide a pulverized toner for developing an electrostatic latent image.

  In view of the above problems, the present inventor has intensively studied to improve the charging performance of the toner when the distance between the magnetic body near the toner surface and the toner surface is small, and the smaller the proportion of toner, the crystallinity. It has been found that when polyester is not present on the toner surface as much as possible, the adhesion of the toner particles is lowered and the fluidity of the toner is improved.

That is, the present invention is a method for producing a pulverized toner for developing an electrostatic latent image, which is used in a magnetic one-component developer containing magnetic powder used in an electrophotographic method and contains a plurality of magnetic toner particles. After mixing a polyester resin, a crystalline polyester, a magnetic powder, a release agent, and a charge control agent, followed by a melt-kneading and pulverizing step of melt-kneading, pulverizing, and classifying, the Tm of the crystalline polyester is 20 ° C. to 40 ° C. A method for producing a pulverized toner for developing an electrostatic latent image, wherein the magnetic toner particles contain a polyester resin and a crystalline polyester in a binder resin, and the crystalline polyester comprises The resin was synthesized using 918 g of 1,4-butanediol, 118 g of 1,6-hexanediol and 1160 g of fumaric acid as raw materials monomers, The blending amount of the crystalline polyester is 15 to 30 parts by mass per 100 parts by mass of the binder resin, the equivalent circle diameter (D) of the magnetic toner particles obtained from a cross section in a transmission electron micrograph, and the magnetic toner. The ratio of the magnetic toner particles satisfying the relationship of L / D ≦ 0.02 as the minimum distance (L) between the particle surface and the magnetic powder surface is 30% or less, and the magnetic toner particle surface The ratio of the magnetic toner particles satisfying A ≧ 0 in the distance (A) between the apex of the convex portion of the magnetic powder present in the vicinity and exposed from the surface of the magnetic toner particles and the surface of the magnetic toner particles is 10% or less. It is a summary.

  According to such a configuration, a pulverized toner for developing an electrostatic latent image that can maintain an appropriate charge amount and an appropriate fluidity, can obtain good image characteristics over a long period of time, and has excellent development stability and fixing performance. Can be provided.

  As described above, according to the present invention, an appropriate charge amount and an appropriate fluidity can be maintained, good image characteristics can be obtained over a long period of time, and development stability and fixing performance can be improved.

FIG. 2 is a cross-sectional view schematically showing the structure of magnetic toner particles constituting the pulverized toner for developing an electrostatic latent image according to the present embodiment.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The electrostatic latent image developing pulverized toner according to this embodiment (hereinafter, also simply referred to as “toner”) is used for a magnetic one-component developer containing magnetic powder used in an electrophotographic system. The toner of the present embodiment contains a plurality of magnetic toner particles, and the magnetic toner particles contain a crystalline polyester in a binder resin.

  The type of the binder resin used in the toner according to the present embodiment is not particularly limited. For example, a styrene resin, an acrylic resin, a styrene-acrylic copolymer, a polyethylene resin, a polypropylene resin, It is preferable to use a thermoplastic resin such as vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, or styrene-butadiene resin. In order to improve the dispersibility of the colorant in the binder resin, the chargeability of the toner, or the fixability of the toner, the binder resin is more preferably a styrene resin or a polyester resin. Hereinafter, the styrene resin and the polyester resin will be described.

  More specifically, the styrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate , Vinyl esters such as vinyl propionate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, N-butyl acrylate, isobutyl acrylate, dodecyl acrylate, N-octyl acrylate, 2-chloroethyl acrylate , (Meth) acrylic esters such as phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide Vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrole N-vinyl compounds such as den and the like. These may be used alone or in combination of two or more with a styrene monomer.

  Moreover, as the polyester resin, any resin obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The following are mentioned as a component used when synthesize | combining a polyester-type resin.

  First, dihydric or trihydric or higher alcohol components include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1, Diols such as 4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, Bisphenols such as hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sol Tan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2, Examples thereof include trivalent or higher alcohols such as 4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  As the divalent or trivalent or higher carboxylic acid component, a divalent or trivalent carboxylic acid, an acid anhydride or a lower alkyl ester thereof is used. Maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid Phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or N-butyl succinic acid, N-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, Divalent carboxylic acids such as alkyl or alkenyl succinic acids such as N-octyl succinic acid, N-octenyl succinic acid, N-dodecyl succinic acid, N-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid; 2,4-benzenetricarboxylic acid (trimellitic acid), 1,2, Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-di Carboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, emporol Examples thereof include trivalent or higher carboxylic acids such as monomeric acids. Moreover, it is preferable that it is 80-150 degreeC, and, as for the softening point of a polyester-type resin, it is more preferable that it is 90-140 degreeC.

  Further, the binder resin may include a thermosetting resin. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100 parts by mass of the thermoplastic resin as the toner binder resin, and it is also preferable to add a crosslinking agent or to partially use a thermosetting resin.

  Therefore, an epoxy resin, a cyanate resin, or the like can be used as the thermosetting resin. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

  Moreover, in this invention, it is preferable that it is 50-65 degreeC, and, as for the glass transition point (Tg) of binder resin, it is more preferable that it is 50-60 degreeC. When the glass transition point is lower than the above range, the obtained toners are fused with each other in the developing device, and the storage stability is lowered. Further, since the resin strength is low, there is a tendency that toner adheres to the photoreceptor. Further, when the glass transition point is higher than the above range, the low-temperature fixability of the toner is lowered. In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC). More specifically, it can be determined by measuring the endothermic curve of the binder resin using a differential scanning calorimeter DSC-6200 manufactured by Seiko Instruments Inc. as a measuring device. Specifically, 10 mg of a measurement sample is put in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point can be determined from the endothermic curve of the obtained binder resin.

  In the present invention, the fixing performance of the toner is remarkably improved by adding the crystalline polyester to the binder resin. As the crystalline polyester, Tm is preferably 90 to 120 ° C, and more preferably 95 to 110 ° C. Mw (weight average molecular weight) is preferably 2000 to 20000, more preferably 4000 to 10000, crystallinity index is preferably 0.6 to 1.5, and 0.8 to 1.0. It is more preferable that

  The compounding amount of the crystalline polyester is preferably 10 to 50 parts by mass and more preferably 15 to 30 parts by mass per 100 parts by mass of the binder resin. If the blending amount of the crystalline polyester is too small, the fixing performance of the toner tends to deteriorate, and if the blending amount of the crystalline polyester is too large, the storage stability of the toner tends to deteriorate.

  The toner according to the exemplary embodiment can be obtained by dispersing various toner compounding agents such as a colorant in a binder resin.

  As the colorant, for example, a pigment such as carbon black or a dye such as acid violet can be used to adjust the color tone. The blending amount of the colorant is preferably 1 to 10 parts by mass per 100 parts by mass of the binder resin.

  Charge control agents are formulated to significantly improve the charge level and charge rise characteristics (indicator of whether to charge to a constant charge level in a short time) and to obtain a toner having excellent durability and stability. is there. That is, when the toner is positively charged for development, a positively chargeable charge control agent is added. When the toner is negatively charged for development, a negatively chargeable charge control agent can be added. .

  The charge control agent is not particularly limited. For example, specific examples of the positively chargeable charge control agent include pyridazine, pyrimidine, pyrazine, all-toxazine, metaoxazine, paraoxazine, and all-to-thia. Gin, metathiazine, parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2, 6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, Azine compounds such as 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline; azine fast Direct dyes composed of azine compounds such as Red FC, Azin Fast Red 12BK, Azin Violet BO, Azin Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW and Azin Dee Black 3RL; Nigrosine, Nigrosine Nigrosine compounds such as salts and nigrosine derivatives; acid dyes comprising nigrosine compounds such as nigrosine BK, nigrosine NB and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; benzylmethylhexyldecylammonium, decyltrimethyl Quaternary ammonium salts such as ammonium chloride can be exemplified, and these can be used alone or in combination of two or more. In particular, the nigrosine compound is optimally used for a positively chargeable toner from the viewpoint of obtaining a quicker charge rising property.

  Further, a quaternary ammonium salt, a carboxylate, or a resin or oligomer having a carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group Examples thereof include resins, styrene-acrylic resins having a carboxyl group, and polyester resins having a carboxyl group.

  In particular, a styrene-acrylic resin having a quaternary ammonium salt as a functional group is optimal from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. In this case, preferred acrylic comonomers copolymerized with the styrene units include methyl acrylate, ethyl acrylate, N-propyl acrylate, iso-propyl acrylate, N-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, N-butyl methacrylate, and iso-butyl methacrylate. As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like ( Lower alkyl) aminoethyl (meth) acrylate; dimethylmethacrylamide, dimethylaminopropylmethacrylamide are preferred. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization. As the charge control agent exhibiting negative chargeability, for example, an organometallic complex and a chelate compound are effective. Examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, and 3,5-di-tert-butylsalicylate chromium. In particular, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The positively or negatively chargeable charge control agent described above is generally in an amount of 0.5 to 15 parts by weight, preferably 0.5 to 8.0 parts by weight, and most preferably 0.5 to 7.0 parts by weight. The toner is preferably contained in the toner (that is, the total amount of toner is 100 parts by mass). If the addition amount of the charge control agent is smaller than the above range, it tends to be difficult to stably charge the toner to a predetermined polarity, and the electrostatic latent image is developed using the toner to develop an image. When the image is formed, the image density tends to decrease or the durability of the image density tends to decrease. In addition, the charge control agent tends to be poorly dispersed, causing so-called fogging, and the contamination of the photoconductor tends to be severe. On the other hand, when the charge control agent is used in a larger amount than the above range, it tends to cause defects such as environmental resistance, particularly poor charging under high temperature and high humidity and defective images, and contamination of the photoreceptor.

  The waxes used for improving the fixing property and the offset property are not particularly limited. For example, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, Fischer-Tropsch wax, paraffin wax, ester It is preferable to use wax, montan wax, rice wax or the like. Two or more of these waxes may be used in combination. By adding such wax, offset property and image smearing can be more efficiently prevented.

  The above-described waxes are not particularly limited, but generally, the wax is preferably blended in the toner (the total amount of the toner is 100 parts by mass) in an amount of 1 to 5 parts by mass. If the addition amount of the wax is less than 1 part by mass, there is a tendency that the offset property and image smearing cannot be efficiently prevented. On the other hand, if it exceeds 5 parts by mass, the toners are fused together. Storage stability tends to decrease.

  The toner of the present invention can be made into a magnetic one-component developer by blending magnetic powder in a binder resin. The toner of the present invention is prepared by mixing the above-described binder resin, crystalline polyester, and various toner compounding agents such as a charge control agent, melt-kneading using a kneader such as an extruder, and cooling the mixture. Obtained by pulverization and classification.

  In general, the toner is preferably classified and adjusted in particle size so that the average particle size is about 5 to 10 μm.

  In the toner of the present invention, the surface of the toner particles can be treated with colloidal silica, hydrophobic silica, titanium oxide, alumina, silicon carbide or the like for the purpose of maintaining the fluidity and storage stability of the toner. Further, these external additives can be surface-treated using aminosilane, chicone oil, hexamethyldisilazane, titanate coupling agent, silane coupling agent or the like, if necessary.

  The silica fine particles and titanium oxide are externally added by dry mixing with magnetic toner. This stirring and mixing is performed so that the fine particles are not embedded in the toner. Etc. are good to use.

  In the toner according to the present embodiment, the ratio of magnetic toner particles satisfying the relationship of L / D ≦ 0.02 obtained as follows is 30% or less, and the magnetic toner particles satisfying A ≧ 0. The ratio is 10% or less.

  A specific method for measuring A, D, and L using a transmission electron microscope in the present invention is, for example, two days in an atmosphere at a temperature of 40 ° C. after sufficiently dispersing a magnetic toner in a room temperature curable epoxy resin. A method of observing the cured product obtained by curing as it is or by freezing and using a microtome as a flaky sample is preferable.

  A specific method for measuring the ratio of the corresponding magnetic toner particles will be described with reference to FIG. That is, the equivalent circle diameter (D) of the magnetic toner particles 1 is obtained from a cross-sectional photograph using a transmission electron microscope, and the value is included in a width of ± 10% of the number average particle diameter of the magnetic toner particles 1. The corresponding magnetic toner particle 1 is used, and the minimum value (L) of the distance between the magnetic toner particle 1 surface and the magnetic powder 2 surface is measured for the corresponding magnetic toner particle 1, and L / D is calculated. Similarly, the distance between the surface of the magnetic toner particle 1 and the apex of the convex portion of the magnetic body 2 that is present near the surface of the magnetic toner particle 1 and that is exposed from the surface of the magnetic toner particle 1 that becomes a charge leak point ( A) is measured. The microphotograph at this time preferably has a magnification of 10,000 to 20,000 times in order to perform highly accurate measurement.

The ratio of particles having an L / D value of 0.02 or less calculated in this way and the ratio of magnetic toner particles satisfying A ≧ 0 are obtained by the following formula.
Proportion of magnetic toner particles satisfying (L / D) ≦ 0.02 = ((the number of magnetic toner particles satisfying (L / D) ≦ 0.02 at the center of the corresponding magnetic toner particles) / (number average of equivalent circle diameter) Number of observed magnetic toner particles corresponding to a width of ± 10% of the particle size)) × 100
Ratio of magnetic toner particles satisfying A ≧ 0 = ((the number of magnetic toner particles satisfying A ≧ 0 at the center of the corresponding magnetic toner particles) / (observation in which the equivalent circle diameter corresponds to a width of ± 10% of the number average particle diameter) Number of magnetic toner particles)) × 100

  In the present invention, the ratio of magnetic toner particles satisfying the relationship of L / D ≦ 0.02 is 30% or less, preferably 20% or less, and more preferably 15% or less. When the ratio of magnetic toner particles satisfying the relationship of L / D ≦ 0.02 exceeds 30%, the ratio of crystalline polyester existing between the magnetic powder and the toner particle surface increases, and this is the starting point. Therefore, toner adhesion tends to occur, and the fluidity of the toner tends to deteriorate.

  In the present invention, the ratio of the magnetic toner particles satisfying A ≧ 0 is 10% or less, preferably 8% or less, and more preferably 5% or less. If the ratio exceeds 10%, charge leakage is likely to occur starting from the convex portion of the magnetic material, so that image density reduction and image defects are likely to occur due to charging failure.

  A heat treatment is preferable as a method of setting the ratio of the magnetic toner particles satisfying A ≧ 0 to 10% or less. The temperature of the heat treatment is preferably higher than the Tm of the crystalline polyester, and specifically, preferably higher than the Tm of the crystalline polyester in the range of 20 ° C. or higher and 40 ° C. or lower.

  As the heat treatment apparatus, for example, saffusion manufactured by Nippon Pneumatic Co., Ltd. is used.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to these examples.

  A polyester resin, a crystalline polyester resin, and a magnetic powder used as a binder resin were prepared according to the following method.

[Preparation of polyester resin]
1960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid and 4 g of dibutyltin oxide were charged into a reaction vessel. Next, the inside of the reaction vessel was placed in a nitrogen atmosphere, and the temperature inside the reaction vessel was raised to 235 ° C. while stirring. Next, the reaction was performed at the same temperature for 8 hours, and then the reaction vessel was depressurized to 8.3 kPA and reacted for 1 hour. Thereafter, the reaction mixture was cooled to 180 ° C., and trimellitic anhydride was added to the reaction vessel to achieve the desired oxidation. Subsequently, the temperature of the reaction mixture was raised to 210 ° C. at a rate of 10 ° C./hour, and the reaction was performed at the same temperature. After completion of the reaction, the contents in the reaction vessel were taken out and cooled to obtain a polyester resin.

[Preparation of crystalline polyester resin A]
After reacting raw material monomers 918 g of 1,4-butanediol, 118 g of 1,6-hexanediol, 1160 g of fumaric acid, 4 g of dibutyltin oxide and 2 g of hydroquinone in a nitrogen atmosphere at 160 ° C. for 5 hours, 200 ° C. Was heated to react for 1 hour to obtain a crystalline polyester resin A. The obtained crystalline polyester resin A had a Tm of 106 ° C., an Mw (average molecular weight) of 5900, and a crystallinity index of 0.9.

[Preparation of crystalline polyester resin B]
Crystalline polyester B was obtained in the same manner as in preparation of crystalline polyester resin A, except that the reaction time was changed from 5 hours to 4 hours. The obtained crystalline polyester resin B had a Tm of 95 ° C., an Mw (average molecular weight) of 4800, and a crystallinity index of 0.9.

[Preparation of magnetic powder]
A ferrous hydroxide colloid obtained by reacting a ferrous salt aqueous solution with 0.80 to 0.99 equivalent of an aqueous alkali hydroxide solution to the ferrous salt of the ferrous salt aqueous solution is included. A first stage reaction in which an oxygen-containing gas is passed through a ferrous salt reaction aqueous solution while heating in a temperature range of 7, 0 to 100 ° C. to produce magnetic particles and nucleation particles, and an iron oxidation reaction When the rate exceeds 50%, an alkali hydroxide solution is added to adjust the pH to 10 or more, and the second stage reaction is performed by bubbling an oxygen-containing gas while heating to a temperature range of 70 to 100 ° C. Based on the octahedron, magnetic iron oxide particles for toner were obtained which consisted of magnetic particles in which the ridges of the hexahedron and octahedron were curved. The obtained magnetic powder had a saturation magnetization of 7.9 Am ² / kg and an average particle size of 0.20 μm.

[Example 1]
35 parts by mass of the polyester resin and 14 parts by mass of the crystalline polyester resin A produced as described above, 45 parts by mass of magnetic powder, 3 parts by mass of wax (Sazol Wax H1, manufactured by Sazol) as a release agent, After mixing 3 parts by mass of a quaternary ammonium salt (Bontron P-51, manufactured by Orient Chemical Co., Ltd.) as a charge control agent with a Henschel mixer (FM20B manufactured by Nippon Coke Industries, Ltd.), a twin screw extruder (Toshiba Machine Co., Ltd.) The mixture was melt kneaded at 130 ° C. with a TEM 45), cooled, and coarsely pulverized with a hammer mill. Further pulverization was performed with a mechanical pulverizer (turbo mill manufactured by Tabo Kogyo Co., Ltd.). Classification was carried out with an airflow classifier, an elbow jet classifier (EJ-LABO, manufactured by Nippon Steel & Mining Co., Ltd.) to obtain a magnetic toner having a volume average particle diameter of 6.8 μm.

Then, it heat-processed at 130 degreeC using the heat processing apparatus (Nihon Pneumatic Co., Ltd. saffusion). A magnetic toner having a volume average particle diameter of 6.8 μm was obtained.
To the toner powder having a volume average particle size of 6.8 μm obtained above, 1.0 part by mass of silica (RA-200H: manufactured by Nippon Aerosil Co., Ltd.) and titanium oxide (EC-100: manufactured by Titanium Industry Co., Ltd.) are added. An evaluation toner was prepared by externally adding 0 part by mass with a Henschel mixer and adhering it to the surface of the magnetic toner powder.

[Example 2]
An evaluation toner was prepared in the same manner as in Example 1 except that the crystalline polyester B was used in place of the crystalline polyester resin A, and the temperature of the heat treatment was changed to 120 ° C.

Example 3
An evaluation toner was prepared in the same manner as in Example 1 except that the heat treatment temperature was changed to 120 ° C.

[Comparative Example 1]
An evaluation toner was prepared in the same manner as in Example 1 except that no heat treatment was performed.

[Comparative Example 2]
An evaluation toner was prepared in the same manner as in Example 2 except that the heat treatment was not performed.

[Comparative Example 3]
An evaluation toner was prepared in the same manner as in Example 2 except that the crystalline polyester resin as a binder resin was not used.

[Comparative Example 4]
An evaluation toner was prepared in the same manner as in Example 1 except that the crystalline polyester resin as the binder resin was not used and no heat treatment was performed.

  Using the toners for evaluation of Examples and Comparative Examples thus obtained and according to the measurement method described above, the ratio of magnetic toner particles satisfying (L / D) ≦ 0.02, and the magnetic toner particles satisfying A ≧ 0 The proportion of was measured. The results are shown in Table 1 below. A transmission electron microscope (manufactured by JEOL Ltd.) was used as an apparatus, observed at a magnification of 20,000 times and an acceleration voltage of 30 kV, and observed and measured using a micrograph having an enlargement magnification of 10,000 times.

  Next, the evaluation toners of the examples and comparative examples are used to evaluate the fluidity evaluation, and the charging characteristics are measured using a page printer (FS-1020D) manufactured by Kyocera as an evaluation machine, and the image characteristics The fixability evaluation was evaluated. In addition, the evaluation method of each characteristic is as follows. These results are also shown in Table 2 below.

<Charging characteristics>
4 parts by mass of the above magnetic toner and 100 parts by mass of a ferrite carrier (FK-150, manufactured by Powdertech) were mixed and triboelectrically charged by a ball mill for 60 minutes in a normal temperature and humidity environment. Thereafter, the charge amount (μC / g) of about 100 mg of the magnetic toner was measured using a charge amount measuring device (Q / M Meter 210HS) manufactured by TREK, and used as the initial charge amount. Further, using the page printer, image formation is performed using the toner for evaluation, and the toner charge amount after 100,000 sheets are continuously fed (printing rate 5%) is set to be the same as the initial charge amount. Measured and used as the amount of charge after durability.

<Image characteristics>
An image evaluation pattern including a solid image is printed by the above page printer at the initial time in a normal temperature and humidity environment (20 ° C., 65% RH) to obtain an initial image. Thereafter, 100,000 sheets are continuously passed, and the image evaluation pattern is again printed. Was printed as an image after durability. A solid image included in each of the initial image and the post-durability image was measured using a Macbeth reflection densitometer (RD914), and image characteristics were evaluated by visually observing character dust and image defects (offset) at the same time. The image density was 1.30 or higher. The following criteria were used for evaluation of character dust and image defects.
(Letter Chile)
○: Character Chile is not seen.
Δ: Some character dust is generated.
X: The character Chile is terrible.
(Image defect)
○: Image defect due to offset is not seen.
Δ: Image defects due to slight offset are observed.
X: Image defect due to offset is severe.

<H / H environmental fog>
The above-described page printer in which the developing toner was filled in each developing toner was left overnight in an H / H environment (35 ° C. × 85%), and then an image evaluation pattern was printed as an initial image to perform initial image evaluation. The fog acceptance criterion was 4 or more.
5: No fogging and image quality is good.
4: Although fog is very slight (allowable range), the image quality is good.
3: A lot of fog occurs, which affects the image quality.
2: Fog is noticeably generated, affecting image quality, and causing a problem.
1: fog is prominent in a wide range, and the image quality is at a problem level and cannot withstand actual use.

<Fixability evaluation>
Set the fixing temperature of the above page printer to 180 ° C, cool it for 10 minutes in the normal environment (20 ° C, 65% RH) with the power off, then turn on the power, and print the fixing pattern solid image continuously 5 sheets Thus, an image for measurement was obtained. This image was reciprocated 10 times with a load of brass weight (1 kg) wrapped with cotton cloth. The image density before and after this operation was measured with a Macbeth reflection densitometer [RD914 manufactured by Gretag Macbeth Co., Ltd.], and the ratio of the density was obtained to determine the fixing property.
○: Fixing rate is 95% or more.
Δ: The fixing rate is 90% or more and less than 95%.
X: Fixing rate is less than 90%.

<Fluidity evaluation>
Using a powder tester (product name) manufactured by Hosokawa Micron Co., Ltd., 10.0 g of each of the evaluation toners left for 12 hours in an environment of a room temperature of 23 ° C. and a relative humidity of 60% is placed on a sieve of 60 μm mesh, and the amplitude is 1 mm and The fluidity was calculated by the following formula by applying vibration for 30 seconds at a frequency of 60 Hz. The lower the value thus obtained, the better the fluidity.
Fluidity (%) = {(mass of toner remaining on the screen (g) /10.0 (g)} × 100
○: Fluidity is less than 20%.
Δ: The fluidity is 20% or more and less than 40%.
X: Fluidity is 40% or more and less than 100%.

  In Examples 1 to 3, the ratio of magnetic toner particles satisfying the relationship of L / D ≦ 0.02 is 30% or less, and the ratio of magnetic toner particles satisfying A ≧ 0 is 10% or less ( (See Table 1), the proper charge amount and proper fluidity were maintained, good image characteristics (image density, image quality) were obtained over a long period of time, and development stability and fixing performance were improved ( (See Table 2).

  On the other hand, in Comparative Examples 1 to 4, the ratio of magnetic toner particles satisfying the relationship L / D ≦ 0.02 exceeds 30%, and the ratio of magnetic toner particles satisfying A ≧ 0 exceeds 10%. Therefore (see Table 1), the proper charge amount and proper fluidity could not be maintained, and good image density could not be obtained over a long period of time (see Table 2). In particular, Comparative Example 3 was inferior in image characteristics (image defects) and fixing performance, and Comparative Example 4 was inferior in image characteristics (character dust, image defects) and fixing performance.

  The present invention can be used as a pulverized toner for developing an electrostatic latent image for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

1 Magnetic Toner Particle 2 Magnetic Powder

Claims (2)

A method for producing a pulverized toner for developing an electrostatic latent image, which is used in a magnetic one-component developer containing magnetic powder used in electrophotography and contains a plurality of magnetic toner particles, comprising: polyester resin and crystalline polyester And a magnetic powder, a release agent, and a charge control agent are mixed, followed by a melt-kneading and pulverizing step of melt-kneading, pulverization, and classification, and then the temperature is higher in the range of 20 ° C. to 40 ° C. than Tm of the crystalline polyester. A method for producing a pulverized toner for developing an electrostatic latent image in which a heat treatment process is performed at a temperature, wherein the magnetic toner particles contain a polyester resin and a crystalline polyester in a binder resin, and the crystalline polyester resin comprises 1,4 -Synthesized by using 918 g of butanediol, 118 g of 1,6-hexanediol and 1160 g of fumaric acid as raw material monomers, The total amount is 15 to 30 parts by mass per 100 parts by mass of the binder resin, the equivalent circle diameter (D) of the magnetic toner particles determined from the cross section in the transmission electron micrograph, the surface of the magnetic toner particles, and the The minimum value (L) of the distance from the surface of the magnetic powder is such that the ratio of the magnetic toner particles satisfying the relationship of L / D ≦ 0.02 is 30% or less, and is present in the vicinity of the surface of the magnetic toner particles. The ratio of the magnetic toner particles satisfying A ≧ 0 in the distance (A) between the apex of the convex portion of the magnetic powder exposed from the surface of the magnetic toner particles and the surface of the magnetic toner particles is 10% or less. A method for producing a pulverized toner for developing an electrostatic latent image. The polyester resin is made by reacting 1960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, and 770 g of terephthalic acid, and then adding trimellitic anhydride so that the desired oxidation is achieved. The method for producing a pulverized toner for developing an electrostatic latent image according to claim 1, wherein the resin is synthesized by further reaction.

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