JP4621509B2 - Toner for electrophotography and method for producing the same - Google Patents

Description

  The present invention relates to an electrophotographic toner used in an electrophotographic method, an electrostatic recording method, and the like, and a method for producing the same.

  In general, an image forming apparatus such as an electrophotographic copying machine or a printer forms an electrostatic latent image on a photoconductive photoconductor, and the electrostatic latent image is rubbed with a carrier or a developing device. After the insulating toner that has obtained triboelectric charge is electrostatically adhered and developed by friction with the charging member constituting the part, and then the formed toner image is transferred to a transfer medium such as plain paper or film The basic principle is to form a copy image or a print image by fixing on a transfer medium by heating, pressing, solvent vapor or the like.

  The electrostatic latent image development method is typified by a two-component development method, a magnetic one-component development method, and a non-magnetic one-component development method. In any of the development methods, the toner is charged and the electrostatic force is applied to the toner. If development is carried on an electrostatic latent image and the toner is not sufficiently charged, not only the toner charge amount will be reduced, but also reversely charged toner particles will be generated, resulting in non-image areas. As a result, there was a problem that the toner adhered to the surface and background fogging occurred on the obtained printed matter.

As described above, the electrophotographic toner to be used needs to be triboelectrically charged by friction with other substances. In order to obtain an appropriate triboelectric charge amount, a charge control agent is generally contained in the past.
Although the charge control agent is a powder, it is agglomerated and agglomerated and inferior in fluidity. It is difficult to loosen even if it is dry-mixed with other materials and heat-melted and kneaded. It is easy to exist in the toner in the state of. If the dispersion of the charge control agent is poor, the content of the charge control agent varies from toner particle to toner particle, and it becomes difficult for the toner particles to be uniformly present on and inside the toner particles, resulting in a broad distribution of charge amount, The rising property of electrification is reduced, causing problems such as increased background fog and toner scattering.
Further, in recent years, high quality images of photographic tone, particularly color photographic tone, have been demanded, and the toner has been reduced in particle size in order to improve image resolving power and fine line reproducibility. As the result, even if the dispersion state in the kneaded composition is the same, the dispersion in the toner particles becomes relatively worse, so the above-mentioned problem becomes remarkable.

To improve the dispersion of the charge control agent, strengthen the kneading conditions. Specifically, for example, lower the kneading temperature to increase the shearing force, reduce the discharge amount of the kneader and knead for a long time. It can be improved by making the screw of the kneader into a pattern with a strong shearing force, etc., but the productivity is inferior, and even if such means is used, sufficient dispersion is not always achieved. When the molecular chain of the high molecular weight component in the resin is cut and fixed by the heat fixing method, a part of the toner adheres to the surface of the heating roller, and the toner is re-transferred onto a transfer medium such as paper. There is a risk that an offset phenomenon that stains the subsequent printed matter or a so-called winding phenomenon in which the transfer medium is wound around the surface of the heating roller, and the fixability on the high temperature side of the toner tends to be lowered. In addition, fusing on the developing roll and charging member, filming on the surface of the photoreceptor, deterioration of toner fluidity, storage stability, and carrier contamination (spent) with two-component developer . Further, the strength of the binder resin was reduced, and the toner was pulverized in the developing machine, causing fogging in the ground or scattering to cause in-machine contamination.
Japanese Patent Laid-Open No. 7-104520 Japanese Patent Laid-Open No. 10-90951 Japanese Patent Laid-Open No. 2-256071 JP 2002-91068 A

The object of the present invention is to improve the charge rise by making the dispersion of the charge control agent good, so that the image density is sufficient from the beginning of printing to after printing a large number of sheets, and background fogging and toner scattering occur. There is no electrophotographic toner to provide.
Another object of the present invention is to provide a method for producing the above electrophotographic toner.

  As a result of intensive studies to improve the dispersion of the charge control agent in the toner and achieve the above-mentioned object, the present inventor has found that the charge control agent can be obtained by using a charge control agent pretreated with inorganic fine particles. It has been found that the dispersion is remarkably improved, and the present invention has been completed.

That is, the electrophotographic toner of the present invention, at least a binder resin, a colorant, and I electrophotographic toner der made by pulverizing a kneaded composition comprising a preprocessed charge control agent in inorganic particles The charge control agent pretreated with the inorganic fine particles is a charge control agent obtained by mixing a charge control agent and inorganic fine particles, and the average primary particle size of the inorganic fine particles is 5 to 100 nm, maximum diameter of the charge control agent in the kneaded composition is Ru 0.3~5.5μm der (claim 1). The ratio of the inorganic fine particles are 2 to 50 wt% with respect to a static-control agent (Claim 2). The inorganic fine particles are silica (Claim 3 ). The content of the charge control agent in the toner is 0.5 to 5.0% by weight (claim 4). The volume average particle diameter of the toner is 3 to 12 [mu] m (Claim 5).
In the method for producing an electrophotographic toner of the present invention, at least 1) agglomerated charge control agent and inorganic fine particles containing hydrophobic silica and having an average primary particle diameter of 5 to 100 nm are charged into a stirrer and stirred. Pretreatment step of charge control agent , 2) Step of preparing a raw material mixture by adding at least a binder resin and a colorant to the pretreated charge control agent, and 3) Hot-melt kneading the raw material mixture And a step of producing a kneaded composition by extrusion, and 4) a step of pulverizing and classifying the kneaded composition to obtain a toner.

  Such an electrophotographic toner of the present invention can be suitably applied to a toner having a small particle diameter. The method for producing an electrophotographic toner of the present invention is suitable for producing a small particle toner.

In the electrophotographic toner of the present invention, the fluidity of the charge control agent is improved by pretreating the charge control agent with inorganic fine particles. As a result, the aggregated particles of the charge control agent are easily crushed, and the charge control agent is controlled. Due to the good dispersion of the agent, even if the particle size is small, the rising of the charge is excellent, so that the image density is sufficient from the beginning of printing until after printing a large number of sheets, causing background fogging and toner scattering. Absent. In addition, since the dispersion of the charge control agent is improved without strengthening the kneading conditions, the molecular chain of the high molecular weight component of the binder resin is not broken, and a part of the toner adheres to the surface of the heating roller. The toner does not cause the offset phenomenon that the toner re-transfers onto the transfer medium such as paper and stains the subsequent printed matter or the so-called wrapping phenomenon that the transfer medium wraps around the surface of the heating roller. Can be improved. Also, fusing with a developing roll or a charging member (for example, a layer thickness regulating blade), filming on the surface of the photoreceptor, deterioration of toner fluidity, storage stability, carrier of two-component developer Contamination (spent) can be prevented. Furthermore, since the decrease in the strength of the binder resin can be suppressed, it is possible to prevent the toner from being pulverized in the developing machine, causing ground fogging, or being scattered and causing internal contamination.
Also, the method for producing an electrophotographic toner of the present invention can provide the electrophotographic toner.

  The toner for electrophotography of the present invention is obtained by pulverizing a kneaded composition containing at least a binder resin, a colorant, and a charge control agent pretreated with inorganic fine particles. Further, it is preferable to add a wax as a releasing agent or a low-temperature fixing agent and other auxiliary agents as necessary. In the case of magnetic toner, it contains magnetic powder. Furthermore, it is preferable to attach inorganic fine particles or resin fine particles to the toner particle surfaces as necessary.

First, the electrophotographic toner of the present invention will be described in detail.
<Binder resin>
As the binder resin in the present invention, a polyester resin, a styrene- (meth) acrylic acid copolymer resin, a thermoplastic elastomer, a styrene resin, a (meth) acrylic resin, an olefin resin (for example, polyethylene, Α-olefin resins such as polypropylene), vinyl resins (for example, polyvinyl chloride, polyvinylidene chloride, etc.), polyamide resins, polyether resins, urethane resins, epoxy resins, polyphenylene oxide resins, terpene phenols Resin, polylactic acid resin, hydrogenated rosin, cyclized rubber, cycloolefin copolymer resin (copolymer of α-olefin and cycloolefin), and the like. These can be used alone or in combination of two or more. Among these, polyester resins and styrene- (meth) acrylic acid copolymer resins are preferable from the viewpoint that the image quality characteristics, durability, productivity, and the like of the toner can be satisfied in a balanced manner. Here, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

Examples of the polyester resin include those obtained by condensation polymerization of alcohol and carboxylic acid.
Examples of the alcohol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butanediol, neopentyl glycol, 1,4 Diols such as butenediol; 1,4-bis (hydroxymethyl) cyclohexane; etherified bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; Valent alcohol monomer. These alcohols may be used alone or in combination of two or more.

  Examples of the carboxylic acid include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, Examples thereof include anhydrides of these acids, dimers of lower alkyl esters and linolenic acid, and other divalent organic acid monomers. These carboxylic acids may be used alone or in combination of two or more.

  The polyester resin may be not only a polymer based on only a bifunctional monomer but also a polymer containing a component based on a trifunctional or higher polyfunctional monomer. Examples of trihydric or higher polyhydric alcohol monomers that are polyfunctional monomers include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, Tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, tri Mention may be made of methylolpropane, 1,3,5-trihydroxymethylbenzene and other trihydric or higher polyhydric alcohol monomers.

Examples of the trivalent or higher polyvalent carboxylic acid monomer include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylene carboxy propane, tetra (methylene carboxyl) methane, 1,2,7,8-octane tetracarboxylic acid, Empol trimer acid, acid anhydrides thereof, naphthenic and other trihydric or higher polycarboxylic acid monomer be able to.
The amount of the trifunctional or higher polyfunctional monomer is 10 to 90 mol, preferably 20 to 80 mol, more preferably 30 to 80 mol, based on 100 mol of the total of the alcohol and carboxylic acid components. Can be selected as appropriate.

Styrene- (meth) acrylic acid copolymer resin can be composed of a copolymer of styrene monomer units and (meth) acrylic acid monomer units, and other monomer units as required. May be contained.
Examples of the styrene monomer include styrene, alkyl styrene (vinyl toluene such as o-methyl styrene, m-methyl styrene, p-methyl styrene, vinyl xylene, pt-butyl styrene, etc.) or derivatives thereof, alkoxy Examples thereof include styrene (such as p-methoxystyrene) or derivatives thereof, p-phenylstyrene or derivatives thereof, halostyrene (such as o-chlorostyrene, m-chlorostyrene, p-chlorostyrene), or derivatives thereof. These monomers can be used alone or in combination of two or more. Examples of the derivatives include alkyl-substituted products, alkylidene-substituted products, alkoxy-substituted products, acyl-substituted products, halogen-substituted products, nitro-substituted products, amino-substituted products, hydroxy-substituted products, and carboxyl-substituted products.

Examples of the (meth) acrylic acid monomer include (meth) acrylic acid, alkyl (meth) acrylate [methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, ( Butyl (meth) acrylate, t-butyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic acid C _1-20 alkyl ester such as behenyl, (meth) acrylic acid C _4-10 cycloalkyl ester], (meth) acrylic acid aryl ester, (meth) acrylic acid C _7-12 aralkyl ester, ( Hydroxyalkyl (meth) acrylate [hydroxyethyl (meth) acrylate, hydroxymeth (meth) acrylate Pills, etc.], (meth) acrylate, glycidyl (meth) dialkylaminoalkyl [dimethylaminoethyl (meth) acrylate acrylate, (meth) acrylic acid diethylaminoethyl], di C _1-4 alkyl phosphate (meth ) Acrylate and the like. These monomers can be used alone or in combination of two or more.

Other monomers include vinyl monomers (vinyl acetate, vinyl propionate, vinyl benzoate, etc.), unsaturated olefin monomers (ethylene, propylene, etc.), diene monomers (isoprene, butadiene, etc.) ), Unsaturated dicarboxylic acids (fumaric acid, maleic acid, itaconic acid, citraconic acid and their anhydrides), (meth) acrylonitrile monomers, (meth) acrylamide monomers, ketones (vinyl methyl ketone) And vinyl hexyl ketone) and ethers (vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc.). These other monomers are preferably contained in 30 parts by weight or less in 100 parts by weight of the styrene- (meth) acrylic acid copolymer resin.
In order to adjust the acid value and charging characteristics, it is preferable to use a monomer containing a carboxyl group or an acid anhydride group such as maleic anhydride and fumaric acid.

As a preferable styrene- (meth) acrylic acid copolymer resin formed by the monomer, a polymer mainly composed of a styrene monomer unit and a (meth) acrylic acid monomer unit, for example, , Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic acid-n-butyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene _Examples thereof include styrene- (meth) acrylic acid C _1-18 alkyl ester copolymers such as methacrylic acid-n-butyl copolymer, and multipolymers such as styrene-acrylic acid ester-methacrylic acid ester.

The content of the binder resin in the electrophotographic toner (100 parts by weight) is preferably 40 to
95 parts by weight, and preferably 80 to 95 parts by weight for a non-magnetic one-component development system.

<Colorant>
Examples of the colorant in the present invention include black pigments for black toners and magenta pigments, cyan pigments, yellow pigments and the like for color toners.
Carbon black is usually used as the black pigment. The number average particle size, oil absorption, PH and the like of carbon black are not particularly limited. Examples of commercially available products include those manufactured by Cabot Corporation of the United States, trade names: REGAL 400, 660, 330, 300, SRF-S, STERLING SO, V, NS, R; manufactured by Columbia Carbon Japan, Product name: Raven H20, MT-P, 410, 420, 430, 450, 500, 760, 780, 1000, 1035, 1060, 1080; manufactured by Mitsubishi Chemical Corporation, product names: # 5B, # 10B, # 40, # 2400B, MA-100 and the like. These carbon blacks can be used alone or in combination of two or more.

The content of carbon black is preferably 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, and still more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin. If the carbon black content is too small, the image density is lowered, and if it is too much, the image quality is liable to be lowered and the dispersibility in the toner particles is also lowered.
As a black pigment, black magnetic powder such as iron oxide and ferrite can be used in addition to carbon black.

Examples of the magenta pigment include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32 , 37 , 38 , 39 , 40 , 41 , 48 , 49 , 50 , 51, 52, 53, 54, 55 , 57, 58, 60 , 63 , 64 , 68 , 81 , 83 , 87 , 88 , 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209; I. Pigment violet 19; C.I. I. Vat red 1 , 2 , 10, 13 , 15 , 23 , 29 , 35 etc. are mentioned. These magenta pigments can be used alone or in combination of two or more.

Examples of cyan pigments include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Bat Blue 6; C.I. I. Acid Blue 45 etc. are mentioned. These cyan pigments can be used alone or in combination of two or more.
Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 94, 97, 155, 180 etc. are mentioned. These yellow pigments can be used alone or in combination of two or more.

  As a color pigment for a full color toner, C.I. I. Pigment Red 57 and 122 are C.I. I. Pigment Blue 15 is C.I. I. Pigment Yellow 17, 93, 155, and 180 can be preferably used.

  The content of the color pigment is usually 1 to 20 parts by weight, preferably 3 to 10 parts by weight, more preferably 4 to 9 parts by weight, and particularly preferably 4 to 100 parts by weight of the binder resin. 5 to 8 parts by weight. When the content of the color pigment is too smaller than the above range, the image density is lowered, and when it is too much, the charging stability is deteriorated and the image quality is liable to be lowered. It is also disadvantageous in terms of cost. As the color pigment, a so-called master batch in which a color pigment is dispersed at a high concentration in a resin that can be a binder resin in advance may be used.

<Charge control agent>
The toner for developing an electrostatic charge image of the present invention needs to contain a charge control agent pretreated with inorganic fine particles.
Examples of positively chargeable charge control agents include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate and tetrabutylammonium tetrafluoroborate Diorganotin oxides such as dibutyltin oxide, dioctyltin oxide and dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate and dicyclohexyltin borate; pyrididium salts, azines, triphenylmethane compounds, cationic functional groups And low molecular weight polymers having These positively chargeable charge control agents may be used alone or in combination of two or more. Among these positively chargeable charge control agents, nigrosine compounds and quaternary ammonium salts are preferably used.

Examples of negatively chargeable charge control agents include acetylacetone metal complexes, monoazo metal complexes, naphthoic acid or salicylic acid metal complexes or salts, organometallic compounds, chelate compounds, low molecular weight polymers having an anionic functional group, and the like. Can be mentioned. These negatively chargeable charge control agents can be used alone or in combination of two or more. Among these negatively chargeable charge control agents, salicylic acid metal complexes and monoazo metal complexes are preferably used.
The content of the charge control agent is usually preferably 0.5 to 5% by weight and more preferably 1 to 4% by weight in the toner.
The charge control agent is preferably colorless or light-colored for color toners.

The charge control agent is usually agglomerated to a size of 1 to 20 μm.
The maximum major axis of the charge control agent in the kneaded composition is preferably 0.3 to 5.5 μm, more preferably 0.5 to 5 μm, further preferably 0.5 to 3 μm, and 0.5 to 1.5 μm. Is particularly preferred.
If the maximum major axis of the charge control agent in the kneaded composition is less than 0.3 μm, the sufficient effect as the charge control agent is lost. If the particle size exceeds 5.5 μm, the variation in chargeability of the toner particles will increase and the rise of charge will be worsened, and the charge control agent will be detached from the toner particles. Arise.

The method for measuring the maximum major axis of the charge control agent in the kneaded composition is as follows.
A section having a cross section perpendicular to the extrusion direction of the sheet-shaped kneaded composition is prepared using a microtome (MT6000, manufactured by Deyupon). This section is observed at a magnification of 400 times using an optical microscope (BHS-SW, manufactured by Olympus Corporation) and photographed. From this photograph, the maximum major axis of the charge control agent is obtained.

<Inorganic fine particles>
The charge control agent needs to be pretreated with inorganic fine particles.
Pretreatment with the inorganic fine particles increases the fluidity of the charge control agent, breaks up the aggregation in the raw material mixing step and the kneading step, and improves the dispersion in the toner.
Examples of the inorganic fine particles include silica, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide and the like. These inorganic fine particles may be used alone or in combination of two or more. Of these inorganic fine particles, silica can be particularly preferably used. Furthermore, the inorganic fine particles are preferably surface-treated and hydrophobic.
The inorganic fine particles are not particularly limited, such as an average particle diameter, a BET specific surface area, and a surface treatment, and can be appropriately selected. The average primary particle diameter is preferably 5 to 100 nm, and more preferably 10 to 30 nm. Also preferably 70~200m ² / g as the BET specific surface area in the range of 50 to 400 m ² / g is more preferable. Those having an average primary particle diameter of less than 5 nm or a BET specific surface area of more than 400 m ² / g are expensive because they are not usually produced because the particle diameter is small. If the average primary particle diameter exceeds 100 nm or the BET specific surface area is less than 50 m ² / g, the fluidity is insufficient and the crushing effect does not increase, and large aggregated particles of the charge control agent remain.

The measurement method of the average primary particle diameter of the inorganic fine particles is as follows.
Using a transmission electron microscope, take an enlarged projection photograph of the fine particles dispersed on the sample support mesh, measure the particle size (average of major and minor axes) of 100 primary particles, and determine the number average particle size. It was.

The method for measuring the BET specific surface area of the inorganic fine particles is as follows.
The BET specific surface area is measured using a high-concentration automatic gas adsorption device (trade name: BELSORP28, manufactured by Nippon Bell Co., Ltd.), and N ₂ gas is used as the adsorption gas. In the measurement, the adsorption amount Vm (cm ³ / g) necessary for forming a monomolecular layer on the surface of the sample is measured, and the BET specific surface area S (m ² / g) is obtained by the following equation.
S = 4.35 × Vm (m ² / g)

  The ratio of the inorganic fine particles to the charge control agent is preferably 2 to 50% by weight, more preferably 3 to 30% by weight, and further preferably 4 to 20% by weight. When the inorganic fine particles are less than 2% by weight, the charge control agent is not sufficiently crushed. If it exceeds 50% by weight, the properties of the toner change.

<Release agent>
The toner for developing an electrostatic charge image of the present invention preferably contains a release agent. Release agents include polyolefin waxes such as polyethylene wax, polypropylene wax and modified polyethylene wax; synthetic waxes such as Fischer-Tropsch wax; petroleum waxes such as paraffin wax and microcrystalline wax; animal waxes such as beeswax and whale wax Plant waxes such as carnauba wax, candelilla wax and rice wax; hardened oils such as hardened castor oil; and mineral waxes such as montan wax, ozokerite and ceresin. These release agents can be used alone or in combination of two or more.

  The content of the release agent is usually about 1 to 20 parts by weight, more preferably 1.5 to 10 parts by weight, and further preferably 1.5 to 7 parts by weight with respect to 100 parts by weight of the binder resin. . When the content of the release agent exceeds 20 parts by weight, the fusion resistance, storage stability and the like may be deteriorated. On the other hand, when the content of the release agent is less than 1 part by weight, the wrapping phenomenon is likely to occur, and the fixing characteristics may be deteriorated.

  At least one of the release agents in the present invention preferably has a melting point measured by a differential scanning calorimeter of 50 to 135 ° C, more preferably 70 to 130 ° C. When the melting point of the release agent is less than 50 ° C., the anti-fusing property and storage stability of the toner may be reduced, and when it exceeds 135 ° C., the low-temperature fixability and fixing strength of the toner may be reduced.

The melting point of the release agent is measured as follows according to ASTM D3418-82.
Approximately 5 mg of a sample is weighed and placed in an aluminum cell, and placed on a differential scanning calorimeter (DSC) (trade name: SCC-5200, manufactured by Seiko Instruments Inc.), and 50 ml of N ₂ gas is supplied per minute. Infuse. The temperature is raised between 0 ° C. and 200 ° C. at a rate of 10 ° C. per minute, held at 200 ° C. for 10 minutes, then lowered from 200 ° C. to 0 ° C. at a rate of 10 ° C. per minute, The temperature is raised for the second time under the above conditions, and the temperature at the top of the maximum endothermic peak at that time is taken as the melting point.

<Magnetic powder>
The electrophotographic toner of the present invention contains magnetic powder in the case of a magnetic toner. In the case of a non-magnetic toner, magnetic powder may be contained as necessary.
Examples of magnetic powder include metals such as cobalt, iron, and nickel; alloys of aluminum, copper, iron, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten, zirconium, and other metals; aluminum oxide And metal oxides such as iron oxide and nickel oxide; ferrite, magnetite and the like. Typical examples are ferrite and magnetite.

The content of the magnetic powder is usually 70 parts by weight or less in the electrophotographic toner (100 parts by weight), and 15 parts by weight or less in the case of the non-magnetic toner. In the case of magnetic toner, it is 15 to 70 parts by weight, preferably 25 to 60 parts by weight.
As magnetic powder, that whose average primary particle diameter is 0.01-3 micrometers can be used conveniently. Moreover, what is necessary is just to select the shape of a magnetic powder suitably as needed, granular, spherical, hexahedron, octahedron, polyhedron, needle shape, and irregular shape.

The measuring method of the average primary particle diameter of magnetic powder is as follows.
Using a transmission electron microscope, take an enlarged projection photograph of the magnetic powder dispersed on the sample support mesh, measure the particle size (average of major axis and minor axis) of 100 primary particles, and calculate the number average particle diameter. Asked.

<External additive>
(Inorganic fine particles)
In the toner for developing an electrostatic charge image of the present invention, it is preferable that inorganic fine particles adhere to the surface for improving fluidity and charging stability. Examples of the inorganic fine particles include silica, alumina, talc, clay, calcium carbonate, magnesium carbonate, titanium oxide, carbon black powder, and magnetic powder. These inorganic fine particles may be used alone or in combination of two or more. Of these inorganic fine particles, silica can be particularly preferably used. Furthermore, surface-treated hydrophobic inorganic fine particles are preferable.
The inorganic fine particles are not particularly limited, such as an average particle diameter, a BET specific surface area, and a surface treatment, and can be appropriately selected. The average primary particle diameter is preferably 5 to 100 nm, and more preferably 10 to 30 nm. Also preferably 70~200m ² / g as the BET specific surface area in the range of 50 to 400 m ² / g is more preferable. Those having an average primary particle diameter of less than 5 nm or a BET specific surface area of more than 400 m ² / g are expensive because they are not usually produced because the particle diameter is small. If the average primary particle diameter exceeds 100 nm or the BET specific surface area is less than 50 m ² / g, the effect of improving the fluidity is insufficient, and the toner particles are easily detached from the toner particles and cause contamination of the photoreceptor.

(Resin fine powder)
The electrophotographic toner of the present invention, in addition to the inorganic fine particles, further, polytetrafluoroethylene resin powder, resin fine powder such as polyvinylidene fluoride resin may be adhered to the surface. The ratio of adding the inorganic fine particles or resin fine powder can be appropriately selected from the range of 0.01 to 8 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 100 parts by weight of the electrophotographic toner. 0.1 to 3 parts by weight. If the added ratio is less than 0.01 parts by weight, there is little effect on the fluidity and charging stability of the toner, and it is difficult to form a uniform image. If it exceeds 8 parts by weight, inorganic fine particles are easily released, It adheres to the photoconductor and the developing machine member and degrades the image quality.

<Toner for electrophotography>
The use of the electrophotographic toner of the present invention is not particularly limited depending on the development method, and can be used in a non-magnetic one-component development method, a magnetic one-component development method, a two-component development method, and other development methods. In the magnetic one-component development system, magnetic powder is mixed with a binder resin and used as a magnetic toner. In the two-component development method, toner is mixed with a carrier and used. In recent years, a one-component development method, particularly a non-magnetic one-component development method is preferred from the viewpoint of simplicity of the apparatus and cost. As described above, the electrophotographic toner of the present invention can make it difficult for the toner to be fused to each member of a developing machine such as a charging member and a developing sleeve, and is suitable for a one-component system.

  As the carrier in the two-component development system, for example, nickel, cobalt, iron oxide, ferrite, magnetite, iron, glass beads and the like can be used. These carriers may be used alone or in combination of two or more. The carrier preferably has an average particle size of 20 to 150 μm. Further, the surface of the carrier may be coated with a coating agent such as a fluorine resin, an acrylic resin, or a silicone resin. Further, a magnetic material dispersed in a binder resin may be used.

  The electrophotographic toner of the present invention may be a monocolor toner or a full color toner, and is particularly preferably used as a full color toner having a small particle size. In the monocolor toner, carbon black or the like can be used as a colorant, and in the full color toner, the color pigment can be used as a colorant.

The volume average particle size of the electrophotographic toner of the present invention is not particularly limited, but is about 3 to 12 μm, preferably 4 to 11 μm, and more preferably 5 to 10 μm. If the volume average particle diameter is less than 3 μm, problems such as poor productivity, increased charge amount and fogging, and relatively deteriorated dispersion of the charge control agent in the toner particles occur. If it exceeds 12 μm, it is difficult to obtain a high-definition image.
The volume average particle diameter is a 50% volume diameter measured using a particle size distribution analyzer (Multisizer II, manufactured by Beckman Coulter, Inc.).

<Method for producing electrophotographic toner>
The method for producing an electrophotographic toner of the present invention comprises at least 1) a step of mixing a charge control agent and inorganic fine particles to produce a pretreated charge control agent, and 2) the pretreated charge control agent, A step of preparing a raw material mixture by adding and mixing at least a binder resin and a colorant, 3) a step of hot-melt kneading the raw material mixture and extruding to prepare a kneaded composition, and 4) a step of preparing the kneaded composition A step of pulverizing and classifying the toner to form a toner, and 5) a step of attaching an external additive to the surface of the toner particles as necessary.

  In the step of obtaining the raw material mixture, first, the charge control agent and the inorganic fine particles are charged into a stirrer such as a turbine stirrer, a Henschel mixer, or a super mixer and stirred. Next, a binder resin, a colorant, and other raw materials as required are added and stirred to obtain a raw material mixture.

Examples of the hot melt kneading method include various methods such as a method using a twin screw extruder, a method using a Banbury mixer, a method using a pressure roller, and a method using a pressure kneader. From the viewpoint of dispersibility and versatility, a method using a twin screw extruder is preferred. The kneaded composition is obtained by hot-melt kneading the raw material mixture with a twin screw extruder and extruding from a die (die) at the tip of the twin screw extruder. The kneading temperature of the twin screw extruder is 70 to 250 ° C, preferably 70 to 200 ° C, more preferably about 90 to 200 ° C.
Examples of the pulverization method include a pulverization method using an apparatus such as a hammer mill, a cutter mill, or a jet mill. Moreover, as a classification method, the method by an airflow classifier like a dry-type centrifugal classifier is mentioned normally.

  In addition, the inorganic fine particles and the resin fine powder described in the above [0043] and [0044] are obtained by stirring the toner particle surface using a stirrer such as a turbine type stirrer, a Henschel mixer, or a supermixer as necessary. It may be attached.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the compounding quantity of a raw material is a weight part.

<Example 1>
・ Raw material combination ・ Charge control agent (Azo-based chromium complex salt, negative chargeability) 3.0 parts (Orient Chemical Industries, trade name: Bontron S-34)
-Hydrophobic silica 0.2 part (Nippon Aerosil Co., Ltd. product name: R972, average primary particle diameter 16 μm, specific surface area 110 m ² / g)
・ Styrene-acrylic acid copolymer resin (Mitsui Chemicals, trade name: CPR100)
89.3 parts polyethylene wax (Hoechst, trade name: PE-130, melting point 130 ° C.)
2.5 parts, carbon black (product name: MA-100, manufactured by Mitsubishi Chemical Corporation) 5.0 parts

The above charge control agent and hydrophobic silica are mixed with a super mixer for 2 minutes, and after the pretreatment of the charge control agent with hydrophobic silica, a styrene-acrylic acid copolymer resin, polyethylene wax, and carbon black are added. Mixing for a minute gave a raw material mixture. Thereafter, the raw material mixture was put into a twin-screw kneader (product name: PCM-65, manufactured by Ikegai Co., Ltd.), melted and kneaded at a set temperature of 120 ° C., extruded at a discharge rate of 90 kg / H, and a thickness of about 1.5 mm. A sheet-like kneaded composition was obtained. The obtained kneaded composition was coarsely pulverized, then pulverized with a jet mill, and classified with a dry air classifier to obtain a toner having a volume average particle size of 9.0 μm. The toner for electrophotography of the present invention (non-magnetic toner) in which 1 part of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd .: trade name: R972) is mixed with a Henschel mixer for 3 minutes to 100 parts of the toner and hydrophobic silica is adhered to the surface. ) The maximum major axis of the charge control agent in the kneaded composition was 1.2 μm.

<Example 2>
・ Raw material combination ・ Charge control agent (Azo-based chromium complex salt, negative chargeability) 3.0 parts (Orient Chemical Industries, trade name: Bontron S-34)
Hydrophobic silica 0.5 part (Nippon Aerosil Co., Ltd. product name: R972, average primary particle size 16 μm, specific surface area 110 m ² / g)
・ Styrene-acrylic acid copolymer resin (Mitsui Chemicals, trade name: CPR100)
54.0 parts polyethylene wax (manufactured by Hoechst, trade name: PE-130, melting point 130 ° C.)
2.5 parts magnetic powder (magnetite) 40.0 parts (manufactured by Toda Kogyo Co., Ltd., trade name: EPT-1000, average primary particle size 0.30 μm, octahedron)
The above charge control agent and hydrophobic silica are mixed with a super mixer for 2 minutes, and after the pretreatment of the charge control agent with hydrophobic silica, a styrene-acrylic acid copolymer resin, polyethylene wax, and magnetic powder are added. Mixing for a minute gave a raw material mixture. Thereafter, the raw material mixture was put into a twin-screw kneader (product name: PCM-65, manufactured by Ikegai Co., Ltd.), melted and kneaded at a set temperature of 120 ° C., extruded at a discharge rate of 90 kg / H, and a thickness of about 1.5 mm. A sheet-like kneaded composition was obtained. The obtained kneaded composition was coarsely pulverized, then pulverized with a jet mill, and classified with a dry air classifier to obtain a toner having a volume average particle size of 9.0 μm. Electrophotographic toner of the present invention (magnetic toner) in which 1 part of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd .: trade name: R972) is mixed with a Henschel mixer for 3 minutes to 100 parts of the toner, and hydrophobic silica is adhered to the surface. Got. The maximum major axis of the charge control agent in the kneaded composition was 1.1 μm.

<Comparative Example 1>
A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that all the raw materials for kneading in Example 1 were simultaneously mixed with a super mixer. The maximum major axis of the charge control agent in the kneaded composition was 7.0 μm.

<Comparative Example 2>
A comparative electrophotographic toner was obtained in the same manner as in Example 1 except that, among the kneading raw materials of Example 1, the other 4 types except for hydrophobic silica were mixed at the same time with a supermixer. The maximum major axis of the charge control agent in the kneaded composition was 7.0 μm.

<Comparative Example 3>
A comparative electrophotographic toner was obtained in the same manner as in Example 2 except that, among the raw materials for kneading in Example 2, the other 4 types except for hydrophobic silica were mixed at the same time with a supermixer. The maximum major axis of the charge control agent in the kneaded composition was 7.1 μm.

<Comparative example 4>
Of the raw materials for kneading in Example 1, the other 4 types except for hydrophobic silica were mixed at the same time with a super mixer, except that the set temperature of the biaxial kneader was 90 ° C. and the discharge rate was 60 kg / H. A comparative electrophotographic toner was obtained in the same manner as in Example 1. The maximum major axis of the charge control agent in the kneaded composition was 1.5 μm.

<Toner evaluation test>
The toners of Example 1 and Comparative Examples 1, 2, and 4 are mounted on a non-magnetic one-component printer (trade name: LP-9200, manufactured by Epson Corporation), and the toners of Example 2 and Comparative Example 3 are used. Mounted on a magnetic one-component copying machine (manufactured by Panasonic Corporation, product name: DP-3200), using A4 transfer paper (68 g / m ² ), and images after initial and after endurance (after 20000 continuous copying) The image density and ground fog were measured as characteristics.
Further, the anti-offset characteristics were evaluated using an external fixing machine.
The evaluation test was conducted in an environment of 20 ° C. and 55% RH.
The measurement results are shown in Table 1.

<Measurement method>
1. Image density (ID)
The density of a solid image of 25 mm × 25 mm was measured with a reflection densitometer (manufactured by Macbeth, trade name: RD914).
2. Ground fog (BG)
A whiteness meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name: MODEL Z-1001DP) was used, and the difference between the whiteness of the non-image area after printing and the whiteness before printing was defined as the value of ground fog.

3. Offset Resistance Using the above printer or copying machine, a strip-shaped unfixed image having a length of 3 cm and a width of 6 cm was prepared on A4 transfer paper (68 g / m ² ). Subsequently, an oilless type fixing machine in which a heat fixing roller having a surface layer formed of polytetrafluoroethylene and a pressure fixing roller having a surface layer formed of silicone rubber are rotated in pairs, and a roller pressure is set to 1 kgf / cm ^2, the roller speed was adjusted to 200 mm / sec, the surface temperature of the heat fixing roller stepwise increased at intervals of 10 ° C. between 120 to 240 ° C., the unfixed image at each surface temperature The toner image on the transfer paper having the toner was fixed. After fixing, observation was made as to whether or not toner contamination occurred in the margin, and a temperature region where no contamination occurred was defined as a non-offset temperature region.

<Evaluation results>
In the electrophotographic toners of the present invention of Examples 1 and 2, the maximum major axis of the charge control agent was 1.5 μm or less and was well dispersed. As a result, the image characteristics were at a level where there was no practical problem with both image density and background fogging both in the initial stage and after the endurance.
On the other hand, the toners of Comparative Examples 1 and 2 had a large dispersion maximum major axis of 7.0 μm and poor dispersion. As a result, the image characteristics had a lot of ground fogging at the initial stage and after the endurance, and could not withstand practical use.
The toner of Comparative Example 3 had a large dispersion maximum major axis of 7.1 μm and the dispersion was poor. As a result, the image characteristics were unsatisfactory for practical use because the image density was low both at the initial stage and after the endurance and there was a lot of ground fog.
The toner of Comparative Example 4 was kneaded over time by lowering the temperature of the biaxial kneader to increase the shearing force, reducing the discharge amount. Accordingly, the maximum major axis of the charge control agent in the kneaded composition was 1.5 μm, which was similar to Example 1 and had the same image characteristics, but the non-offset temperature on the high temperature side was low.

  Examples and Comparative Examples will be described supplementarily using schematic diagrams of the electron micrographs and optical micrographs of FIGS. 1 to 4, as shown in FIG. Although the charge control agent can be seen as large particles, as shown in FIG. 2, the pre-treated charge control agent of Example 1 has hydrophobic silica adhered to the entire surface of the charge control agent particles. I understand that. 3 is an optical micrograph of the kneaded composition of Example 1, it can be seen that the charge control agent is well dispersed as small particles, FIG. 4 is an optical micrograph of the kneaded composition of Comparative Example 2, It can be seen that the charge control agent remains agglomerated as large particles.

The electrophotographic toner of the present invention is suitable for all development systems, transfer systems, and fixing systems. It can be applied to both mono color and full color. It can also be applied to small toner particles. It can also be applied to special uses (for example, for MICR).
The method for producing an electrophotographic toner of the present invention can produce the electrophotographic toner.

2 is a schematic diagram of an electron micrograph of an untreated state of the charge control agent used in Example 1. FIG. 2 is a schematic diagram of an electron micrograph after pretreatment of the charge control agent used in Example 1. FIG. 2 is a schematic diagram of an optical micrograph of the kneaded composition of Example 1. FIG. 6 is a schematic diagram of an optical micrograph of a kneaded composition of Comparative Example 2. FIG.

Claims (6)

An electrophotographic toner obtained by pulverizing a kneaded composition containing at least a binder resin, a colorant, and a charge control agent pretreated with inorganic fine particles, wherein the charge control agent pretreated with the inorganic fine particles is A charge control agent obtained by mixing a charge control agent and inorganic fine particles, the inorganic fine particles include hydrophobic silica, and the average primary particle diameter of the inorganic fine particles is 5 to 100 nm, and the kneading composition electrophotographic toner maximum diameter of the charge control agent in the object is characterized 0.3~5.5μm der Rukoto. 2. The toner for electrophotography according to claim 1, wherein the ratio of the inorganic fine particles to the charge control agent is 2 to 50% by weight. The toner for electrophotography according to claim 1 or 2, wherein the inorganic fine particles are silica. The toner for electrophotography according to any one of claims 1 to 3, wherein the content of the charge control agent is 0.5 to 5.0 wt%. The toner for electrophotography according to any one of claims 1 to 4, wherein the volume average particle diameter of 3 to 12 [mu] m. At least 1) a charge control agent pretreatment step in which agglomerated charge control agent and inorganic fine particles containing hydrophobic silica and having an average primary particle diameter of 5 to 100 nm are charged into a stirrer and stirred; A step of preparing a raw material mixture by adding and mixing at least a binder resin and a colorant to the treated charge control agent; 3) a step of hot-melt kneading and extruding the raw material mixture to produce a kneaded composition; And 4) a step of pulverizing and classifying the kneaded composition to obtain a toner, and a method for producing an electrophotographic toner.

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