JP2007034223A - Electrostatic charge image developing toner and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing toner capable of forming an image of high quality stably for a long period without the occurrence of a cleaning defect even with the toner of high circularity and without depending on an environment and printing pattern, and an image forming method. <P>SOLUTION: The electrostatic charge image developing toner externally added with at least silica particles is ≥0.98 in the mean circularity of the toner and is characterized in that the aggregated particles of the silica particles are prepared by mixing silica particles (I) having a peak within a range of 7 to 14 nm and silica particles (II) having a peak within a range of 50 to 300 nm in a primary particle size distribution and subjecting the mixture thereof to wet process treatment with a silane coupling agent and/or silicone oil and that the above aggregated particles have one peak within a range of 3 to 10 μm in the volume reference particle size distribution by a laser diffraction type grain size distribution meter. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrostatic charge image developing toner used in an image forming apparatus such as a copying machine or a printer using an electrophotographic method or an electrostatic recording method, and an image forming method using the same.

In image forming apparatuses such as printers and copiers, toner with high sphericity is used to improve transfer efficiency and image quality.
Silica particles or the like may be added as an external additive for the purpose of obtaining good developability, cleaning properties, and transferability by adjusting the charging stability, durability stability, environmental stability, and fluidity of the toner. Generally known. The externally added silica particles have a function of stabilizing the chargeability of the toner and suppressing adhesion between the toners.
However, such a toner having externally added silica particles having a small particle diameter, when used for a long time, is embedded in the surface due to stress caused by contact with a carrier or stirring in a developing device. There is a problem that it is easy to do.
In this case, in order to reduce the burying of the external additive having a small particle size, it is effective to use the external additive having a large particle size together. The external additive with a large particle size reduces the friction of the external additive with a small particle size on the toner surface with the charge imparting blade, contact with the carrier, or contact with the inner wall of the developing unit or a stirring blade. Therefore, the burying of the external additive having a small particle diameter can be suppressed, and the life of the toner can be extended.

In Patent Documents 1 to 3 and the like, toners that define the particle diameter of the external additive and have excellent development stability are proposed. In Patent Documents 1 and 2, paying attention to the function due to the difference in particle size of the external additive, transferability is improved in one silica fine powder having a different particle size, and fluidity is imparted to the toner in the other silica fine powder. The main purpose is to use an external additive composed of two types of silica having different primary particle diameters. In this proposal, the primary particle size distribution is specified, and the particle size distribution of the aggregated particles in which the primary particles are aggregated is also specified. As the external additive, the characteristics are exhibited even by the aggregated particles that are originally in an aggregated state together with the primary fine particles, and therefore it is necessary to define the particle size distribution in the aggregated particles. Further, Patent Document 3 proposes an improvement in transfer surname by defining an aggregated particle diameter for silica as an external additive.
JP 2004-126250 A JP 2004-145325 A JP 2004-212520 A

A cleaning blade is generally used as a cleaning means for residual toner on the electrostatic image carrier and transfer means, and the externally added silica particles form a layer on the cleaning blade. There is a function to suppress slipping through. However, in the case of using a toner having a high sphericity that is sharp and provides high image quality, the spherical toner tends to pass through the cleaning blade and easily cause poor cleaning. For this reason, it is possible to improve the cleaning property by using particles having a relatively large particle size that can easily form a blocking layer with a cleaning blade as an external additive. Further, the chargeability of the toner can be adjusted by using particles having a relatively small particle diameter, and the adhesion between the toners can be reduced.
However, when the particle diameter of the silica particles is relatively large and the particle size distribution is wide, the adhesion to the toner varies even though the cleaning property is good. This variation in adhesion is difficult to eliminate even with the use of external additives having different particle diameters, and there is a problem that good cleaning performance cannot be maintained.
The toner described in Patent Document 1 externally adds two types of silica fine powders having different primary average particle diameters, but the two types of silica are not completely dispersed because the aggregation state level of silica is also different. In addition, the amount of silica adhered varies among toner particles, and stable cleaning properties and toner charging properties cannot be obtained.
In addition, although the toners described in Patent Documents 2 to 3 define the aggregated particle diameter of silica, the influence of the primary particle diameter is not taken into consideration, so that both the cleaning property and the charging property of the toner can be satisfied. Can not.
Therefore, an object of the present invention is to develop an electrostatic charge image that can stably form a high-quality image over a long period of time without depending on the environment and print pattern without causing poor cleaning even with toner having a high degree of circularity. Toner and an image forming method using the same are provided.

  As a result of intensive research to solve the above-mentioned problems, the present inventor mixed two types of silica particles having different primary particle size distributions, and then hydrophobized them to form agglomeration in which both were uniformly dispersed. By using particles having a predetermined peak value in the particle size distribution as external additives, it was newly found that stable cleaning properties can be secured in any printing environment, and the present invention has been completed. .

That is, the electrostatic image developing toner and image forming method of the present invention have the following configurations.
(1) An electrostatic charge image developing toner in which at least silica particles are externally added to toner particles composed of at least a binder resin, a colorant, and a release agent, and the average circularity of the toner is 0.98 or more. In the primary particle size distribution, silica particles (I) having a peak in the range of 7 to 14 nm and silica particles (II) having a peak in the range of 50 to 300 nm are mixed, and this is mixed with a silane coupling agent and The agglomerated particles of silica particles obtained by wet treatment with silicone oil have one peak in the range of 3 to 10 μm in the volume-based particle size distribution measured by a laser diffraction particle size distribution meter. Toner for developing electrostatic images.
(2) An image forming method having a charging step, an exposure step, a developing step, and a transfer step along the moving direction of the electrostatic image carrier, wherein the toner used in this image forming method is at least a binder resin, An electrostatic image developing toner in which at least silica particles are externally added to toner particles composed of a colorant and a release agent. The toner has an average circularity of 0.98 or more and a primary particle size distribution of 7 to 7 Silica particles (I) having a peak in the range of 14 nm and silica particles (II) having a peak in the range of 50 to 300 nm are mixed, and this is wet-treated with a silane coupling agent and / or silicone oil. The agglomerated particles of the silica particles have a peak in the range of 3 to 10 μm in the volume-based particle size distribution by a laser diffraction particle size distribution meter. Image forming method according to symptoms.

  According to the electrostatic image developing toner of the present invention and the image forming method using the same, by using aggregated particles composed of a plurality of silica particles having different primary particle diameters as external additives, good chargeability can be maintained. In addition to making use of the functions unique to each primary particle size, such as ensuring cleaning properties, the function of agglomerated primary particles, such as ensuring long-term stability, is added to ensure stable cleaning properties in any printing environment. be able to.

  The electrostatic image developing toner according to the present invention will be described. The electrostatic image developing toner used in the present invention is a toner containing at least silica particles as an external additive. The toner has an average circularity of 0.98 or more and a primary particle size distribution within 7 to 14 nm. Silica particles (I) having a peak in the range and silica particles (II) having a peak in the range of 50 to 300 nm are mixed, and this is treated with a hydrophobizing agent such as a silane coupling agent and / or silicone oil. The toner is characterized in that the agglomerated particles of silica particles obtained by wet treatment have a peak in the range of 3 to 10 μm in a volume-based particle size distribution measured by a laser diffraction particle size distribution meter. .

トナーの外添剤として用いるシリカ粒子は、トナーの帯電性を含めてトナーに働く付着力の安定化を担う機能に加え、感光体ドラム／ベルトや転写ドラム／ベルト上の転写残トナーの回収を補助する機能がある。この作用は回収に使用されるクリーニングブレードに外添剤の層が形成されることにより、トナーのクリーニングブレードからのすり抜けを抑制するものである。転がりやすくてクリーニングブレードに層を形成しにくく、また付着力が高くてすり抜けを起こしやすい球形のトナーにおいては、クリーニング性を高める上で、外添剤の層形成が必須である。 In general, the higher the average circularity of the toner, the closer to a sphere, the better the fluidity, the better the transfer efficiency, and the easier it is to maintain the image density. However, on the other hand, charging adjustment becomes difficult and slipping through the cleaning blade easily occurs, resulting in poor cleaning.
Here, the average circularity is measured using a flow type particle image analyzer, the circularity of the measured particles is obtained by the following equation, and the total circularity of all the measured particles is the total number of particles. The divided value is defined as the average circularity.

Silica particles used as an external additive for toner, in addition to the function of stabilizing the adhesion force acting on the toner including the chargeability of the toner, collects the residual toner on the photosensitive drum / belt and transfer drum / belt. There is a function to assist. This action suppresses slipping of toner from the cleaning blade by forming a layer of an external additive on the cleaning blade used for recovery. In the case of a spherical toner that easily rolls and hardly forms a layer on the cleaning blade, and has a high adhesive force and easily slips through, it is essential to form a layer of an external additive in order to improve cleaning properties.

For forming the external additive layer, silica particles (II) having a primary particle diameter of 50 to 300 nm, which is relatively easily detached from the toner, are effective as the external additive. Those having a primary particle diameter exceeding 300 nm are very easily detached from the toner particles and contaminate the toner carrier. Further, when the primary particle diameter is smaller than 50 nm, the layer on the cleaning blade is difficult to be formed as described above.
On the other hand, the silica particles (I) having a primary particle diameter of 7 to 14 nm are essential for maintaining the reduction in adhesion, including the chargeability of the toner, and are therefore preferably used in combination with the silica particles (II).

  In other words, the functions of the silica particles (I) and (II) are that the silica particles (I) maintain the chargeability of the toner and impart fluidity, and the silica particles (II) improve the cleaning performance for the toner. is there. It is difficult to obtain these functions with a single silica particle, and it is possible to mix the silica particles (I) and (II) according to the present invention and use them as hydrophobized silica particles. A high-quality image can be formed over a long period of time in any printing environment, and a stable cleaning action can be obtained.

When two types of silica particles having different primary particle diameters are used in combination, the amount of the silica particles (II) having a primary particle diameter of 50 to 300 nm tends to vary among toner particles. For this reason, it is preferable to mix with the 7-14 nm silica particle (I) used together and to perform a coupling process wet. By mixing and wet-treating, silica powder in which both are uniformly dispersed is obtained. By using this as an external additive, variation in the amount of silica particles (II) deposited between the toner particles can be suppressed and uniformized.
The silica powder obtained by the wet treatment is composed of agglomerated particles in which silica particles are aggregated, and is pulverized by a pulverizer or the like, and the particle size distribution on a volume basis by a laser diffraction type particle size distribution meter is in the range of 3 to 10 μm. It is preferable to use a fine powder having one peak inside.

When the peak value is less than 3 μm, it is technically difficult. When the peak value exceeds 10 μm, the charge imparting property to the toner is lowered, and fog or toner tends to be scattered in the developing device. This is not preferable because the abundance of silica particles varies among particles and transferability deteriorates.

(External additive)
Examples of the external additive used in the present invention include silica. Along with silica, for example, titanium oxide, alumina, or the like may be used. Examples of the silica powder include Aerosil RA200H, NAY200, NA50H, R972, R974, 90, Silica D-17, T-805, R-812, RA200, HRX-C manufactured by Nippon Aerosil Co., Ltd .; TG820F, TG824F manufactured by Cabot Corporation Cab-o-SilM-5, MS-7, MS-75, HS-5, EH-5, S-17, TS-72; KE-E30 and KE-E40 manufactured by Nippon Shokubai Co., Ltd.

  The silica particles are prepared by mixing the silica particles (I) and (II) in a solvent such as toluene, and adding a silane coupling agent and / or silicone oil to the solution for hydrophobization, and then irradiating with ultrasonic waves. While stirring, stir. Next, the solid obtained by distilling off the solvent is dried and heat-treated to form a powder, which is pulverized by a pulverizer such as a jet mill, Preferably, a powder having one peak in the range of 3 to 10 μm can be obtained.

As the silane coupling agent used for the hydrophobization treatment, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, Benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethyl Ethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltet Lamethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethyl containing Si-bonded hydroxyl groups, each having 2 to 12 siloxane units per molecule, one for each terminal unit Polysiloxane etc. are mentioned.
It may be treated with a nitrogen-containing silane coupling agent, and is particularly preferable in the case of a positively chargeable toner. Examples of nitrogen-containing silane coupling agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxy Silane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltrimethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl -Γ-propylbenzylamine, trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmolybdenum Holin include trimethoxysilyl -γ- propyl imidazole. These treatment agents can be used alone or in a mixture of two or more, or in combination or in multiple treatments.

  In addition, examples of the silicone oil used for the hydrophobing treatment together with the silane coupling agent or independently include those represented by the following structural formula (1).

[式中、Ｒ₁からＲ₁₀は、同じでも異なっていてもよく、水素、水酸基、アルキル基、アリール基、フェニル基、置換基を有するフェニル基、脂肪酸基、ポリオキシアルキレン基またはパーフルオロアルキル基、ハロゲンを示し、ｍおよびｎは整数を示す。]
好ましいシリコーンオイルとしては、一般的なストレートシリコーンオイルとしてジメチルシリコーンオイル、メチルフェニルシリコーンオイル、メチルハイドロジェンシリコーンオイル、および変性シリコーンオイルであるメタクリル変性シリコーンオイル、アルキル変性シリコーンオイル、エポキシ変性シリコーンオイル、脂肪酸変性シリコーンオイル、フッ素変性シリコーンオイル等が挙げられ、また側鎖に窒素原子を有するシリコーンオイルを用いても良く、特に、正帯電性トナーの場合は側鎖に窒素原子を有するシリコーンオイルを用いることが好ましい。

[In the formula, R ₁ to R ₁₀ may be the same or different, and are hydrogen, hydroxyl group, alkyl group, aryl group, phenyl group, phenyl group having a substituent, fatty acid group, polyoxyalkylene group or perfluoroalkyl. Group and halogen, and m and n are integers. ]
Preferred silicone oils include dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, and modified silicone oils such as methacryl-modified silicone oil, alkyl-modified silicone oil, epoxy-modified silicone oil, and fatty acid as general straight silicone oils. Modified silicone oil, fluorine-modified silicone oil, and the like may be used, and a silicone oil having a nitrogen atom in the side chain may be used. In particular, in the case of a positively charged toner, a silicone oil having a nitrogen atom in the side chain should be used. Is preferred.

(toner)
The toner used in the present invention can be obtained by adding a release agent, a colorant, and a charge control agent to a predetermined amount of a binder resin, and stirring and mixing the mixture with a mixing device such as a Henschel mixer. The mixture obtained by stirring and mixing is melt-kneaded with a twin screw extruder or the like, cooled, and then pulverized with a pulverizer such as a hammer mill or a jet mill. Next, after classification using a classifier such as an air classifier, toner particles having a predetermined average particle diameter and high average circularity are obtained by a thermal spheronizer. Next, the obtained toner particles can be manufactured by adding a predetermined amount of the external additive and stirring and mixing with a mixing device such as a Henschel mixer.

(Binder resin)
The binder resin is not particularly limited. For example, styrene-acrylic resin, polyester resin, polyacrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin. Examples thereof include thermoplastic resins such as resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Of course, if necessary, other resins may be used in combination with these resins, or two or more of these resins may be used.

  Examples of the monomer serving as the base of the styrene-acrylic resin include styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, pt-butylstyrene, p-chlorostyrene, and hydroxystyrene; methacrylic acid, Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, methoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate , Ethoxydiethylene glycol (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, (meth) acrylonitrile, (meth ) Acrylamide, N-methylol (meth) acrylamide, ethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, trimethylol ethanetri (meth) Examples include (meth) acrylic acid esters such as acrylate.

  The mixture of the above various monomers can be polymerized by any method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., to obtain a binder resin used in the present invention. In the polymerization, usable polymerization initiators include acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2 , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile and other known polymerization initiators can be used. These polymerization initiators are preferably used in the range of 0.1 to 15% by weight based on the total weight of the monomers.

  The polyester resin is mainly obtained by polycondensation of polyvalent carboxylic acids and polyhydric alcohols. Examples of the polyvalent carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, succinic acid, 1, 2 , 4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, pyromellitic acid and other aromatic polycarboxylic acids; maleic acid, fumaric acid, succinic acid, adipic acid Aliphatic dicarboxylic acids such as sebacic acid, malonic acid, azelaic acid, mesaconic acid, citraconic acid and glutaconic acid; cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid and methylmedicic acid; anhydrides and lower alkyl esters of these carboxylic acids 1 type or 2 types or more of these are used.

  Here, the content of the trivalent or higher component depends on the degree of cross-linking, and the addition amount may be adjusted in order to obtain a desired degree of cross-linking. In general, the content of trivalent or higher components is preferably 15 mol% or less.

  Examples of the polyhydric alcohol used in the polyester resin include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, neopentyl glycol, 1 Alkylene glycols such as 1,5-pentane glycol and 1,6-hexane glycol; alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol and polytetramethylene glycol; 1,4-cyclohexane Aliphatic polyhydric alcohols such as dimethanol and hydrogenated bisphenol A; bisphenols such as bisphenol A, bisphenol F, and bisphenol S, and bisphenols It can be mentioned alkylene oxide adducts can be used in combination of two or more thereof.

  For the purpose of adjusting the molecular weight and controlling the reaction, monocarboxylic acid and monoalcohol may be used as necessary. Examples of the monocarboxylic acid include benzoic acid, paraoxybenzoic acid, toluene carboxylic acid, salicylic acid, acetic acid, propionic acid, and stearic acid. Examples of the monoalcohol include monoalcohols such as benzyl alcohol, toluene-4-methanol, and cyclohexanemethanol.

  The glass transition temperature of the binder resin is preferably in the range of 54 to 62 ° C. This is because if the glass transition temperature is less than 54 ° C., the toner may be hardened in the developing device or the toner cartridge, and if it exceeds 62 ° C., the toner may not be sufficiently fixed on the transfer object such as paper.

(Release agent)
The release agent used for improving the fixing property and the offset property is not particularly limited. For example, polyethylene wax, polypropylene wax, Teflon (registered trademark) wax, Fischer-Tropsch wax, paraffin wax, It is preferable to use ester 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 (dirt around the image when the image is rubbed) can be more efficiently prevented.

  The wax described above is not particularly limited, but is preferably blended in an amount of 1 to 10 parts by mass with respect to the total amount of the binder resin. If the addition amount of the wax is less than 1 part by mass, there is a tendency that offset property and image smearing cannot be effectively prevented. On the other hand, if the addition amount exceeds 10 parts by mass, the toners are fused and stored. There is a tendency for stability to decrease.

(Coloring agent)
The colorant that is a pigment is not particularly limited. For example, black colorants such as acetylene black, lanblack, aniline black, and other carbon blacks; magenta colorants that are described in the color index . I. Pigment red 81, C.I. Pigment Red 122, C.I. I. Pigment red 57, C.I. Pigment Red 49, C.I. I. Solvent Red 49, C.I. I. Solvent Red 19, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15; C.I. I. Pigment blue 15, C.I. I. Pigment blue 15-1, C.I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 86, C.I. I. Direct Blue 25: Nitro pigments such as naphthol yellow S, yellow pigments, azo pigments such as Hansa Yellow 5G, Hansa Yellow 3G, Hansa Yellow G, Benzidine Yellow G, Vulcan Fast Yellow 5G, or yellow iron oxide, ocher Inorganic pigments such as C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 16, C.I. I. Solvent Yellow 19, C.I. I. Solvent yellow 21 etc. are mentioned. One or more of these colorants may be used in combination. These colorants are blended in a proportion of 2 to 20 parts by mass, preferably 3 to 15 parts by mass with respect to the total amount of the binder resin.

(Charge control agent)
Conventionally known charge control agents can be used as the charge control agent. Examples of the positively chargeable charge control agent include nigrosine dyes, fatty acid-modified nigrosine dyes, carboxyl group-containing fatty acid-modified nigrosine dyes, quaternary ammonium salts, amine compounds, and organometallic compounds. Examples of the negatively chargeable charge control agent include metal complexes of oxycarboxylic acids, metal complexes of azo compounds, metal complex dyes and salicylic acid derivatives.
The above-described positively or negatively chargeable charge control agent is preferably contained in the toner at a ratio of 1 to 15 parts by mass with respect to the total amount of the binder resin. 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 this toner to develop an image. When forming, 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 toner according to the present invention can be used as a one-component developer composed only of toner or a two-component developer composed of toner and carrier. In particular, since it can be suitably used in a full-color image forming method, it is preferably used as a two-component developer.

(Career)
To obtain a two-component developer, the toner and the carrier may be mixed. Examples of the carrier include glass beads, oxidized or unoxidized iron powder, ferrite, Co-based, Mn-Mg-based, Cu-Zn-based. , Li-based magnetic particles, or those whose surfaces are covered with a synthetic resin (acrylic, fluorine-based, silicone-based, polyester-based resin, etc.). Among them, it is particularly preferable to use a core whose surface is coated with a fluorine epoxy resin or a silicone resin. As a result, the durability of the carrier can be improved and a good image can be formed over a longer period of time.
Such a carrier preferably has a volume-based center particle size of 30 to 100 μm, more preferably 30 to 65 μm. The carrier concentration of the two-component developer is preferably 2 to 15% by weight.
It can also be used as a binder type carrier in which magnetic powder is dispersed in a binder resin. This is characterized by low magnetization, low specific gravity, high electrical resistance, small particle size and the like, and is suitable for a carrier for high image quality development because of a relatively high degree of freedom in selecting materials and composition ratios.

(Magnetic powder)
Examples of the magnetic powder include triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), iron oxide zinc (ZnFe ₃ O ₄ ), and iron yttrium oxide (Y ₃ Fe ₅ O). _12), iron oxide cadmium (CdFe2O4), iron oxide gadolinium (Gd3Fe5O12), oxidized iron-copper (CuFe ₂ O _4), oxidation Tetsunamari (PbFe ₁₂ O _19), iron oxide nickel (NiFe ₂ O _4), iron oxide neodymium (NdFeO ₃ ), iron barium oxide (BaFe ₁₂ O ₁₉ ), iron magnesium oxide (MgFe ₂ O ₄ ), iron oxide manganese (MnFe ₂ O ₄ ), iron lanthanum oxide (LaFeO ₃ ), iron powder (Fe), cobalt Examples thereof include powder (Co) and nickel powder (Ni). A particularly suitable magnetic powder is particulate iron trioxide (magnetite). A suitable magnetite is a magnetite having a regular octahedral shape and a particle diameter of 0.05 to 1.0 μm. The magnetite particles may be surface-treated with a silane coupling agent, a titanium coupling agent, or the like. The content of the magnetic powder is preferably 1 to 3 parts by weight with respect to 100 parts by weight of the binder resin.

(Image forming method)
An image forming method according to an embodiment of the present invention will be described with reference to the drawings using an example using a two-component developer. FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention. An image forming apparatus 1 according to an embodiment of the present invention includes an electrostatic charge image carrier drum 2 that is rotationally driven in the direction of arrow A in FIG. Around the electrostatic charge image carrier drum 2, there are a charging device 3, an exposure device 4, developing devices 5Y, 5M, 5C and 5K for yellow, magenta, cyan and black, and an intermediate transfer member roller in the order of the image forming process. 6 and a cleaning blade 7 are disposed. These developing devices 5Y, 5M, 5C and 5K contain a two-component developer composed of toner and carrier.
At the time of image formation, the electrostatic charge image carrier drum 2 is uniformly charged by the charging device 3, and the surface of the electrostatic charge image carrier drum 2 is irradiated from the exposure device 4 to form an electrostatic latent image. It is formed. This electrostatic latent image is formed for each color, and a developer of a color corresponding to each electrostatic latent image is supplied from the developing devices 5Y, 5M, 5C, and 5K, and a toner image is formed for each color to carry an electrostatic image. The image is once transferred onto the intermediate transfer body roller 6 that contacts the body drum 2. A color image is formed on the intermediate transfer roller 6 by superimposing the images of the respective colors. A transfer roller 9 is provided below the intermediate transfer body roller 6 so as to be pressed against the photosensitive drum 2, and when the recording paper P is conveyed to the nip portion between the intermediate transfer body roller 6 and the transfer roller 9. Further, the color image on the intermediate transfer body roller 6 is transferred to the recording paper P.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited only to a following example.

Silicas A to L were prepared according to the following formulation, and toners A to M were prepared using the silicas. Table 1 shows the average particle diameter of the silica particles (I) and (II) used and the parts by weight used.

(Preparation of hydrophobic silica A)
Aerosil 300 (average primary particle size 7.0 nm: manufactured by Nippon Aerosil Co., Ltd.) 0.58 parts by weight as silica particles (I) in toluene and KE-E30 (average primary particle size 300 nm: Nippon Shokubai Co., Ltd.) as silica particles (II) 1.5 parts by weight and 3 parts by weight of dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) were stirred for 30 minutes while being irradiated with ultrasonic waves at room temperature. Subsequently, toluene was distilled off using a rotary evaporator, and the obtained solid was dried with a vacuum dryer at a set temperature of 50 ° C. until it was not reduced. Furthermore, heat treatment was performed at 200 ° C. for 3 hours in a nitrogen stream in an electric furnace. The obtained powder is pulverized by a jet mill, thereby agglomerating silica having a peak at 5.5 μm (hereinafter referred to as agglomerated particle peak) in a volume-based particle size distribution by a laser diffraction particle size distribution meter. Hydrophobic silica A composed of particles was obtained.

(Preparation of hydrophobic silica B)
Except for changing the silica particles (II) to 0.25 parts by weight of Aerosil OX50 (average particle diameter 50 nm: manufactured by Nippon Aerosil Co., Ltd.) and adjusting the peak of the aggregated particles to 5.6 μm, Hydrophobic silica B was obtained.

(Preparation of hydrophobic silica C)
Same as hydrophobic silica A, except that the silica particles (I) were changed to 1.33 parts by weight of Aerosil 130 (average primary particle size 13.2 nm: manufactured by Nippon Aerosil Co., Ltd.) and the peak of the aggregated particles was adjusted to 5.4 μm. Thus, hydrophobic silica C was obtained.

(Preparation of hydrophobic silica D)
Silica particles (I) are aerosil (average primary particle size 13.2 nm: manufactured by Nippon Aerosil Co., Ltd.) 1.33 parts by weight, silica particles (II) are Aerosil OX50 (average particle size 50 nm: manufactured by Nippon Aerosil Co., Ltd.) 0.25 Hydrophobic silica D was obtained in the same manner as hydrophobic silica A, except that the weight parts were changed and the aggregated particle peak was adjusted to 6.2 μm.

(Preparation of hydrophobic silica E)
Hydrophobic silica E was obtained in the same manner as hydrophobic silica A, except that the aggregate particle peak was adjusted to 2.9 μm.

(Preparation of hydrophobic silica F)
Hydrophobic silica F was obtained in the same manner as hydrophobic silica A, except that the aggregated particle peak was adjusted to 10.1 μm.

(Preparation of hydrophobic silica G)
The silica particles (II) were changed to 0.2 parts by weight of Aerosil 50 (average primary particle diameter: 40 nm, manufactured by Nippon Aerosil Co., Ltd.), and the aggregated particle peak was adjusted to 5.7 μm. Hydrophobic silica G was obtained.

(Preparation of hydrophobic silica H)
The silica particles (II) were changed to 2.0 parts by weight of KE-E40 (average primary particle size 400 nm: manufactured by Nippon Shokubai Co., Ltd.), and the same as in the case of hydrophobic silica A, except that the aggregate particle peak was adjusted to 5.7 μm. Thus, hydrophobic silica H was obtained.

(Preparation of hydrophobic silica I)
Hydrophobic silica I was obtained in the same manner as hydrophobic silica A, except that the aggregate particle peak was adjusted to 26.9 μm.

(Preparation of hydrophobic silica J)
Silica particles (I) were changed to 1.33 parts by weight of Aerosil 130 (average primary particle size 13.2 nm: manufactured by Nippon Aerosil Co., Ltd.), silica particles (II) were not used, and the peak of aggregated particles was adjusted to 5.8 μm. Except that, hydrophobic silica J was obtained in the same manner as hydrophobic silica A.

(Preparation of hydrophobic silica K)
The silica particles (I) were not used, and the silica particles (II) were changed to 0.25 parts by weight of Aerosil OX50 (average primary particle size 50 nm: manufactured by Nippon Aerosil Co., Ltd. ) , and the peak of the aggregated particles was adjusted to 6.7 μm. Produced hydrophobic silica K in the same manner as hydrophobic silica A.

(Production method of hydrophobic silica L)
In a 75 L Henschel mixer, 0.58 parts by weight of Aerosil 300 (average primary particle size 7.0 nm: manufactured by Nippon Aerosil Co., Ltd.) as silica particles (I) and KE-E30 (average primary particle size 300 nm: silica particles (II)) 1.5 parts by weight (manufactured by Nippon Shokubai Co., Ltd.) was mixed and stirred, and the inside of the Henschel mixer was replaced with a nitrogen atmosphere. After spraying 5 parts by weight of dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) heated at 200 ° C., heat treatment was performed at 350 ° C. in an electric furnace. The obtained powder was crushed by a jet mill to obtain hydrophobic silica L composed of silica agglomerated particles having a peak at 5.2 μm in a volume-based particle size distribution by a laser diffraction particle size distribution meter.

(Preparation of Toner A)
The binder resin is 100 parts by weight of tufton NE-382 (manufactured by Kao Corporation) as a polyester-based resin, 4 parts by weight of carnauba wax No. 1 (manufactured by Hiroyuki Kato), and carbon black as a colorant. 12 parts by weight and 1 part by weight of Pontron P-51 (manufactured by Orient Chemical Co., Ltd.) as a charge control agent were respectively charged and mixed in a Henschel mixer, melted and kneaded with a twin screw extruder, and cooled with a drum flaker. Next, coarsely pulverized with a hammer mill, then finely pulverized with a turbo mill, classified using an air classifier, and then spherical at 280 ° C. using a thermal spheronizer (Nippon Pneumatic Co., Ltd., SFS type 3). To obtain toner particles having a volume average particle size of 6.44 μm and an average circularity of 0.988. To 100 parts by weight of the toner particles, 2 parts by weight of hydrophobic silica A as an external additive was added and mixed with high stirring with a Henschel mixer to obtain a toner. This was mixed with a ferrite carrier having an average particle diameter of 35 μm and surface-coated with a fluorine epoxy resin so that the toner concentration was 8 parts by weight of the carrier, and the developer was prepared by stirring and mixing uniformly with a Nauter mixer. This was designated as Toner A.

(Preparation of toners B to I)
Toners B to I were obtained in the same manner as the toner A, except that the hydrophobic silica A was changed to hydrophobic silicas B to I, respectively.
(Production of toners J and K)
Toners J and K were obtained in the same manner as toner A, except that the hydrophobic silica A was changed to 1.33 parts by weight of hydrophobic silica J and K, respectively.

(Preparation of toner L)
A toner L was obtained in the same manner as in the toner A except that the hydrophobic silica A was changed to the hydrophobic silica L.
(Preparation of Toner M)
Toner M was obtained in the same manner as Toner J, except that 1.33 parts by weight of hydrophobic silica J were changed to 1 part by weight of hydrophobic silica J and 0.25 parts by weight of hydrophobic silica K.

（平均一次粒子径）
〔シリカ粒子の平均一次粒径の測定方法〕本発明においてシリカ粒子の平均一次粒径の測定は、フィールドエミッション走査電子顕微鏡（日本電子社製 ＪＳＭ−７７００Ｆ）により１０万倍に拡大したトナー粒子表面の写真を撮影し、その拡大写真を必要に応じてさらに拡大して行い、それぞれの粒子について５０個以上の粒子について定規、ノギス等を用い、その個数平均粒径を測定した。
(凝集粒径)
シリカ粒子の凝集粒径は、堀場製作所社製レーザ回折/散乱式粒子径分布測定装（ＬＡ−５００）にてエタノール溶媒中で測定した。測定装置の測定系内に試料液を徐々に加えて、装置の画面上のＰＩＤＳ（濃度）が４５〜５５％になるように測定系内の試料濃度を調整して測定を行い、体積分布から算術した分布から頻度比率を求めた。
測定温度としては２０℃〜２５℃の範囲で行った。
(帯電量)
帯電量は、トレック・ジャパン社製ｑ／ｍメーター(ＭＯＤＥＬ ２１０ＨＳ)を用いて、６３５メッシュ(目開き２０μm)により測定した。 <Measurement of average circularity, average particle size, aggregated particle size and charge amount>
With respect to the toner particles and silica particles obtained above, the average circularity, average particle diameter, aggregated particle diameter and charge amount were measured by the following methods.
(Average circularity)
The average circularity of the toner particles was measured using a flow type particle image analyzer FPIA-2000 manufactured by Sysmex Corporation, and the circularity corresponding to the cumulative particle size value at 50% of the circularity represented by the following formula was used.

(Average primary particle size)
[Measuring Method of Average Primary Particle Size of Silica Particles] In the present invention, the average primary particle size of silica particles is measured by the surface of toner particles magnified 100,000 times by a field emission scanning electron microscope (JSM-7700F manufactured by JEOL Ltd.). The enlarged photograph was further enlarged as necessary, and the number average particle diameter of each particle was measured using a ruler, calipers, etc. for 50 or more particles.
(Agglomerated particle size)
The agglomerated particle size of the silica particles was measured in an ethanol solvent using a laser diffraction / scattering particle size distribution measuring device (LA-500) manufactured by Horiba. Gradually add the sample solution into the measurement system of the measurement device, adjust the sample concentration in the measurement system so that the PIDS (concentration) on the screen of the device is 45 to 55%, and measure the volume distribution. The frequency ratio was calculated from the arithmetic distribution.
The measurement temperature was 20 ° C to 25 ° C.
(Charge amount)
The charge amount was measured with a 635 mesh (aperture 20 μm) using a q / m meter (MODEL 210HS) manufactured by Trek Japan.

画像濃度および画像かぶり濃度は、グレタグマクベス社製スペクトロアイ反射濃度計を用いて測定を行った。ＩＳＯ５%連続２０万枚印字を行った際に、画像濃度については、１．２以上であることを合格とし、画像かぶり濃度については、０．００８以下であることを合格とした。
クリーニング性は、ＩＳＯ５%連続２０万枚印字行った後に、画像上の筋の発生有無により判断し、筋が発生していない場合を○、発生した場合を×とした。 <Evaluation test>
[Examples 1-6, Comparative Examples 1-7]
A color printer (trade name “FS-C5016N”) manufactured by Kyocera Mita Co., Ltd., which employs a two-component development system, is loaded with any of the toners A to M produced above, and image density, fog, and cleaning during printing Sexuality was evaluated. As for image density, image fog density, charge amount, and cleaning property, an ISO image pattern was printed at a rate of 5% (hereinafter referred to as ISO 5%) and ISO 5% was printed on a continuous 200,000 sheets. The results are shown in Table 2.

The image density and the image fog density were measured using a spectroeye reflection densitometer manufactured by Gretag Macbeth. When 200,000 sheets of ISO 5% continuous printing was performed, the image density was determined to be 1.2 or higher, and the image fog density was determined to be 0.008 or lower.
The cleaning performance was judged by the presence or absence of streaks on the image after 200,000 sheets of ISO 5% continuous printing was performed.

(Examples 1-6)
As shown in Table 2, in Examples 1 to 6, the average primary particle size of the silica particles (I) is 7.0 to 13.2 nm, the silica particles (II) is 50 to 300 nm, and the aggregate particle size of silica is 3 10 μm and hydrophobized by a wet method. After printing 200,000 sheets of ISO 5% continuously, the image density is 1.31 to 1.38, which satisfies the acceptance standard 1.20, and is fogged. Was 0.002 to 0.005 and satisfied the acceptance standard of 0.008 or less. All the cleaning properties were acceptable without any streaks.

(Comparative Examples 1 to 3)
Primary particle size of silica particles (I) and silica particles (II), and volume-based particle size by laser diffraction type particle size distribution meter after mixing silica particles (I) and silica particles (II) and wet processing Since the distribution did not satisfy the predetermined value, a good image could not be obtained and a cleaning failure sometimes occurred.
(Comparative Example 4 to Comparative Example 5)
Since hydrophobic silica obtained by wet-treating either one of silica particles (I) and silica particles (II) was used, a good image could not be obtained and a cleaning failure sometimes occurred.
(Comparative Example 6, Comparative Example 7)
Since hydrophobic silica that has been dry-processed or hydrophobic silica that has been separately wet-processed with silica particles (I) and silica particles (II) is used, good images may not be obtained and poor cleaning may occur. there were.

  As described above, silica particles (I) and (II) are mixed and silica agglomerated particles obtained by wet hydrophobization treatment are used, so that stable cleaning can be achieved without causing poor cleaning even in high-circularity toners. It can be seen that a high-quality image is formed.

1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Electrostatic charge image carrier drum 3 Charging apparatus 4 Exposure apparatus 5Y, 5M, 5C, 5K Developing apparatus 6 Intermediate transfer body roller 7 Cleaning blade 9 Transfer roller

Claims (2)

An electrostatic image developing toner in which at least silica particles are externally added to toner particles comprising at least a binder resin, a colorant, and a release agent,
The toner has an average circularity of 0.98 or more;
Silica particles (I) having a peak in the range of 7 to 14 nm in the primary particle size distribution and silica particles (II) having a peak in the range of 50 to 300 nm are mixed, and this is mixed with a silane coupling agent and / or Aggregated particles of the silica particles obtained by wet treatment with silicone oil have one peak in the range of 3 to 10 μm in the volume-based particle size distribution measured by a laser diffraction particle size distribution meter. Toner for image development. An image forming method having a charging step, an exposure step, a development step, and a transfer step along the moving direction of the electrostatic image carrier,
The toner used in this image forming method is an electrostatic charge image developing toner in which at least silica particles are externally added to toner particles composed of at least a binder resin, a colorant, and a release agent.
The toner has an average circularity of 0.98 or more;
Silica particles (I) having a peak in the range of 7 to 14 nm in the primary particle size distribution and silica particles (II) having a peak in the range of 50 to 300 nm are mixed, and this is mixed with a silane coupling agent and / or Aggregated particles of the silica particles wet-treated with silicone oil have one peak in the range of 3 to 10 μm in the volume-based particle size distribution by a laser diffraction particle size distribution meter. Method.

Images