JP2010145471A - Electrostatic latent image developing carrier, two component developer, and image forming process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing carrier for maintaining the charge providing ability in a preferable range without change even at the wear of a carrier covered with a resin due to friction stress in a developing device, a developer, and an image forming process using the same. <P>SOLUTION: The electrostatic latent image developing carrier includes resin covering layer in which at least the magnetic particle surface is covered with resin. The resin covering layer includes silicone resin particles of a 200-5,000 nm number average primary particle size by 5-60 mass% with respect to the total mass of the resin covering layer in a resin layer including an acrylic resin as the main component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a carrier for developing an electrostatic latent image, a developer using the carrier, and an image forming method.

  In conventional image formation by an electrostatic latent image forming method such as an electrophotographic method, an electrostatic latent image is formed on an electrophotographic photosensitive member or an electrostatic latent image recording body using various means. A method of forming a toner image by attaching colored particles called toner to the toner and developing the electrostatic latent image is used.

  During this development, carrier particles called a carrier for developing an electrostatic latent image (sometimes simply referred to as a carrier) are mixed with the toner, and both are frictionally charged with each other to impart an appropriate amount of positive or negative charge to the toner. is doing. Carriers are roughly classified into carriers having a coating layer made of resin on the surface and carriers not having a coating layer on the surface. In consideration of the life of the developer, the carrier having the coating layer is superior. Therefore, carriers having various types of coating layers have been developed and put into practical use.

  Although there are various characteristics required for the carrier, it is ultimately required to stably apply an appropriate charge to the toner and to maintain the appropriate and stable chargeability over a long period of time. For this purpose, the carrier has suitable electrical properties, has resistance to environmental changes such as humidity and temperature, has high impact resistance and friction resistance, and changes its ability to impart electrification over the long term. It is important not to do so, and various carriers have been proposed.

  However, there is an advantage that the life of the developer can be extended by the carrier. However, when this is used for a long time, the wear of the coating layer is caused by the stress due to friction in the apparatus, and the decrease in the toner charge amount is observed. . Therefore, in order to stabilize long-term charging, there is a need for a coating layer that is devised so as not to cause a decrease in the charge amount of the toner even when stressed by friction.

  On the other hand, in the image forming method, currently, reversal development is mainly performed using a negatively chargeable organic photoreceptor, and therefore, a method of combining a negatively chargeable toner with this is widely used.

  In this case, there are various types of resins used for the carrier coating layer, but acrylic resins have a strong ability to give negative charge to the toner as compared with other resins, and can be said to be extremely preferable coating resins in that sense. In addition, the surface strength is low and the toner tends to wear due to friction with the toner or the like (see, for example, Patent Document 1).

On the other hand, in the apparatus, small particles such as toner adhering or external additives separated from the toner adhere to the surface of the carrier due to friction with the toner. The toner and the external additive adhering to the carrier surface hinder the contact between the carrier surface and the new toner, so that the charging performance and its stability are lowered. Therefore, in order to scrape off deposits on the surface of the carrier, there has been proposed a carrier whose surface has a coating layer structure that is easily scraped by friction with toner or an external additive in the apparatus (for example, Patent Documents 2 to 4). reference). However, with the above-described configuration alone, sufficient durability cannot be obtained when used for a long period of time, and stable print production cannot be performed.
Japanese Patent No. 3939639 Japanese Patent No. 39731313 Japanese Patent No. 3998793 Japanese Patent No. 3928124

  The present invention has been made to solve the above problems.

  As described above, in order to prevent adhesion of toner, external additives, etc., the coating layer usually made of resin must be worn. However, when the resin coating layer is worn down and the film thickness is reduced, the charge imparting ability of the carrier is also lowered, so that the toner charge amount is lowered. Therefore, there is also a need for a measure for preventing the charge imparting ability from deteriorating when the carrier is used for a long time.

  That is, the object of the present invention is for developing an electrostatic latent image, in which the charge imparting ability does not change even when the resin-coated carrier is worn due to frictional stress in the developing device and can be kept in a good range. It is an object to provide a carrier, a developer, and an image forming method using the same.

  As a result of extensive studies by the inventors of the present invention, it has been found that the object of the present invention can be achieved by adopting the following configuration.

  1. In an electrostatic latent image developing carrier having a resin coating layer in which at least the magnetic particle surface is coated with a resin, the resin coating layer has a number average primary particle size of 200 to 5000 nm in a resin layer mainly composed of an acrylic resin. An electrostatic latent image developing carrier comprising 5 to 60% by mass of silicone resin particles based on the total mass of the resin coating layer.

  2. 2. The electrostatic latent image developing carrier as described in 1 above, wherein undulations having a height difference of 0.5 to 1.5 [mu] m are present on the surface of the resin coating layer.

  3. The electrostatic latent image according to 1 or 2 above, wherein the electrostatic latent image developing carrier has a volume average particle diameter of 20 to 70 μm, and an average film thickness of the coating layer is 1.5 to 4.0 μm. Carrier for developing latent images.

  4). 4. The electrostatic latent image developing carrier according to any one of 1 to 3, wherein the resin coating layer is produced by a dry coating method.

  5. In the two-component developer comprising at least a binder resin and a toner containing a colorant and a carrier, the carrier is a carrier for developing an electrostatic latent image having a resin coating layer in which at least the magnetic particle surface is coated with a resin, The resin coating layer contains 5 to 60% by mass of silicone resin particles having a number average primary particle system of 200 to 5000 nm based on the total mass of the resin coating layer in a resin layer mainly composed of an acrylic resin. Two-component developer characterized.

  6). 6. An image forming method, wherein the electrostatic latent image is developed using the two-component developer described in 5 above.

  According to the present invention, even when a resin-coated carrier is worn by receiving a frictional stress in a developing device, the charge imparting ability does not change and the carrier for developing an electrostatic latent image can be maintained in a favorable range. And an image forming method using the same.

  Whether the excellent effects of the present invention can be obtained by the configuration of the present invention can be understood by considering the following.

  In the present invention, the resin coating layer on the carrier contains silicone resin particles, and by utilizing the difference in hardness between the fine particles and the acrylic resin, the surface of the resin coating layer has a minute height difference of 0.5 to 1.5 μm. Make swell exist. When the carrier coating resin is depleted, the acrylic resin is more easily depleted than the silicone fine particles, so that it has a deteriorating effect and the resin coating layer is not scraped below its size due to the hardness of the silicone resin particles. For this reason, even if the device is subjected to friction stress and wears, the charge imparting ability of the resin coating layer containing the charge control particles is maintained in a favorable range, and the carrier has high durability and long life.

  By including high-strength silicone resin particles in the resin coating layer, even if the weak acrylic resin is scraped, it will not be scraped beyond the height of the silicone resin particles, and the acrylic resin will disappear and the charge amount of the toner will decrease. Can be prevented. Furthermore, since the surface of the silicone resin particles has low activity, toner adhesion can be prevented. Even if the acrylic resin is scraped, toner adhesion can be prevented, and a double prevention effect can be considered.

  Considering the combination of the coating resin and the fine particles contained in the layer, resins other than acrylic resins have insufficient chargeability to the toner, and resin particles other than silicone do not have sufficient strength, so it is urgent. The effect of the present invention will not be obtained.

  The compound used in the present invention, its constitution, and the image forming method will be further described.

[Magnetic particles (core material)]
Examples of the magnetic particles used in the present invention include iron powder, magnetite, various ferrite particles, or those in which they are dispersed in a resin. Magnetite and various ferrite particles are preferred. As the ferrite, ferrite containing heavy metals such as copper, zinc, nickel and manganese and light metal ferrite containing alkali metals and / or alkaline earth metals are preferable.

The saturation magnetization is preferably 2.5 × 10 ^{−5 to} 15.0 × 10 ⁻⁵ Wb · m / kg.

  The saturation magnetization is measured by “DC magnetization characteristic automatic recording device 3257-35” (manufactured by Yokogawa Electric Corporation).

[Resin layer]
The resin suitable for forming the resin coating layer of the electrostatic charge image developing carrier of the present invention may be any acrylic resin that can impart an appropriate charge amount to the toner. Specifically, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacrylic acid Methacrylic acid ester derivatives such as lauryl acid, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic acid Polymers obtained from acrylate derivatives such as isobutyl, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc. It can gel. Furthermore, for these methacrylic acid ester and acrylic acid ester monomers, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4- Dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, p- Styrene such as n-decylstyrene or pn-dodecylstyrene or a styrene derivative may be copolymerized. In this case, it is desirable that the methacrylic acid ester or acrylic acid ester component is contained in an amount of 60% by mass or more of the entire resin.

  The average thickness h of the resin layer is preferably 1.5 to 4.0 μm from the viewpoint of achieving both carrier durability and low resistance. The average thickness h of the resin layer is a value calculated by the following method.

  Regarding the method of measuring the film thickness, a carrier flake is produced with a focused ion beam sample preparation device (SMI2050 manufactured by SSI Nano Technology Co., Ltd.), and then the cross section of the flake is subjected to a transmission electron microscope (JEM-2010F JEOL). (Manufactured by Co., Ltd.) was observed with a field of view of 5000 times, and the average value of the part having the maximum film thickness and the part having the minimum film thickness in the field of view was defined as the average thickness h of the resin layer.

  In addition, the volume average particle diameter of a carrier is 20-70 micrometers, Preferably it is 30-60 micrometers. This volume average particle diameter is a volume-based average particle diameter measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympatech) equipped with a wet disperser.

[Measurement of undulation height difference]
In the present invention, a scanning probe microscope (SPM) can be used.

  A scanning probe microscope is a general term for microscopes that detect interaction force (tunnel current, atomic force, electromagnetic force, etc.) acting between a probe and a sample, and perform surface shape observation and physical property analysis of a minute region.

  For example, by using a scanning probe microscope system SPI3800N and a multi-function unit SPA400 manufactured by Seiko Instruments Inc., the surface shape can be visualized by contact AFM or dynamic force mode, and the surface undulation can be measured.

  Specifically, Matsunami micro slide glass (product number s1226 thickness 1.0 mm) is cut into 10 mm x 10 mm, and the same amount of Nichiban epoxy strong adhesive Araldite standard main component and polyamidoamine curing agent are used on the surface. Mix and apply as thin as possible with a spatula. After leaving at 25 ° C. for 5 hours, the sample was uniformly sprinkled so that the carrier particles as a dispersion were dispersed, and cured at 25 ° C. for 7 hours.

  By fixing the adhesive or pressure-sensitive adhesive, about 2/3 to 1/2 of the particle diameter of each particle of the carrier was exposed on the adhesive or pressure-sensitive adhesive on average.

  This was placed on a sample stage and measured by a dynamic force mode (DFM) of a scanning probe microscope system SPI3800N manufactured by Seiko Instruments Inc. and a multifunctional unit SPA400. The cantilever uses SI-DF20 (made of silicon, spring constant of about 20 N / m, resonance frequency 135 kHz) manufactured by Seiko Instruments, and the scanner measures the shape using FS-100N.

  The scanning areas were 100 μm × 100 μm and 20 μm × 20 μm, and the scanning speed was 1 Hz. As a result, the whole particle and the shape of the vertex of the particle can be clearly measured. As a result, in-plane waviness (surface height difference) is measured.

  By utilizing the difference in hardness between the silicone resin particles and the acrylic resin, minute undulations with a resin coating layer surface height difference of 0.5 to 1.5 μm are present.

[Silicone resin particles]
The silicone resin particles according to the present invention preferably have a three-dimensionally crosslinked siloxane skeleton. In particular, those using alkyltrialkoxysilane and having a three-dimensional crosslinked structure are preferred. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and a methyl group is preferable. Furthermore, examples of the alkoxy group include a methoxy group and an ethoxy group.

  As the silicone fine particles, those having a number average primary particle size of 200 to 5000 nm are used. The number average primary particle diameter is measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.). Further, a true spherical shape can be preferably used.

  Specifically, commercially available products having trade names such as Tospearl 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.) can be used.

[Production of resin layer]
Specific methods for producing the resin layer include a wet coating method and a dry coating method. Each method is described in detail below.

As a wet coating method,
(1) Fluidized bed type spray coating method A method in which a coating solution in which a coating resin is dissolved in a solvent is spray-coated on the surface of magnetic particles using a fluidized bed and then dried to produce a coating (2) Immersion type coating Method A method in which magnetic particles are immersed in a coating solution in which a coating resin is dissolved in a solvent, followed by drying, and then dried to produce a coating. (3) Polymerization method In a coating solution in which a reactive compound is dissolved in a solvent Examples include a method in which magnetic particles are immersed and applied, and then a heat treatment is applied to perform a polymerization reaction to produce a film.

As dry coating method,
A method in which a resin particle is deposited on the surface of a particle to be coated, and then a mechanical impact force is applied, and the resin particle deposited on the surface of the particle to be coated is melted or softened and fixed, thereby producing a coating. It is. Using a high-speed stirring mixer that can impart mechanical impact force to magnetic particles (core material), resin, charge control particles, and low-resistance fine particles without heating or under heating, the impact force is repeatedly applied to the mixture by high-speed stirring. The carrier is applied by being dissolved and softened on the surface of the magnetic particle to be fixed. When heating, 60-125 degreeC is preferable. This is because if the heating temperature is excessive, aggregation of carrier particles tends to occur.

[Carrier resistance]
The resistance of the carrier used in the present invention is 1 × 10 ^{8 to} 3 × 10 ¹⁰ Ωcm, more preferably 2 × 10 ⁸ to 1 × 10 ¹⁰ Ωcm.

[Measurement of carrier resistance]
The carrier resistance is a resistance that is dynamically measured under developing conditions with a magnetic brush. An aluminum electrode drum having the same dimensions as the photosensitive drum is replaced with a photosensitive drum, particles are supplied onto the developing sleeve to form a magnetic brush, and the magnetic brush is rubbed against the electrode drum. By applying a voltage (500 V) between them and measuring the current flowing between them, the resistance of the carrier particles was determined by the following equation.

DVR (Ωcm) = (V / I) × (N × L / Dsd)
DVR: Carrier resistance (Ωcm)
V: Voltage between developing sleeve and drum (V)
I: Measurement current value (A)
N: Development nip width (cm)
L: Development sleeve length (cm)
Dsd: Distance between developing sleeve and drum (cm)
In the present invention, measurement is performed at V = 500 V, N = 1 cm, L = 6 cm, and Dsd = 0.06 cm.

(Developer)
The toner constituting the two-component developer of the present invention can contain, for example, a binder resin and a colorant.

  The method for producing such a toner is not particularly limited, and is known as a pulverization method, a suspension polymerization method, a miniemulsion polymerization aggregation method, an emulsion polymerization aggregation method, a dissolution suspension method, a polyester molecular extension method, or the like. The method of etc. can be mentioned. In particular, the image forming method of the present invention can form an image with good image quality stably over a long period of time because even an irregular toner can be charged with high uniformity over a long period of time. it can.

(Suspension polymerization method)
The suspension polymerization method is performed as follows. That is, a toner constituent component such as a release agent or a colorant and a radical polymerization initiator are added to the radical polymerizable monomer, and then these are dissolved or dispersed in the radical polymerizable monomer by a sand grinder or the like. Then, a uniform monomer dispersion is prepared, and then the monomer dispersion is added to an aqueous medium to which a dispersion stabilizer has been added in advance, and the monomer dispersion is prepared by homomixer or ultrasonic dispersion. Disperse in an aqueous medium to form oil droplets. Since the particle size of the oil droplets finally becomes the particle size of the toner, the oil droplets are controlled and dispersed so as to have a desired particle size. The size of the oil droplets to be dispersed is preferably 3 to 10 μm in volume-based median diameter. Thereafter, the mixture is heated and polymerized, and after completion of the polymerization reaction, the dispersion stabilizer is removed, washed and dried to obtain colored particles, and external additives are added and mixed as necessary to obtain toner particles. Can do.

[Binder resin]
When the toner particles constituting the toner are produced by a pulverization method, a dissolution suspension method, or the like, as the binder resin constituting the toner, a styrene resin, a (meth) acrylic resin, a styrene- (meth) acrylic resin is used. Various known resins such as copolymer resins, vinyl resins such as olefin resins, polyester resins, polyamide resins, polycarbonate resins, polyethers, polyvinyl acetate resins, polysulfones, epoxy resins, polyurethane resins, urea resins, etc. These resins can be used. These can be used alone or in combination of two or more.

  Toner particles can be obtained by adding a release agent, a colorant, or the like to these binder resins, kneading using a biaxial kneader or the like, and then pulverizing and classifying.

  On the other hand, when the toner particles constituting the toner are produced by suspension polymerization method, miniemulsion polymerization aggregation method, emulsion polymerization aggregation method, etc., as a polymerizable monomer for obtaining each resin constituting the toner, For example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethyl Styrene or styrene derivatives such as styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene; Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, Methacrylate derivatives such as isobutyl tacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, acrylic Acrylic acid ester derivatives such as phenyl acid; olefins such as ethylene, propylene, isobutylene; vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinyl fluoride Vinyl halides such as vinyl; vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone N-vinyl compounds such as N-vinylcarbazole, N-vinylindole and N-vinylpyrrolidone; Vinyl compounds such as vinylnaphthalene and vinylpyridine; Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide And vinyl monomers such as These vinyl monomers can be used alone or in combination of two or more.

  Moreover, it is preferable to use combining what has an ionic dissociation group as a polymerizable monomer. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate And 3-chloro-2-acid phosphooxypropyl methacrylate.

  Furthermore, as a polymerizable monomer, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl A binder resin having a crosslinked structure can also be obtained using a polyfunctional vinyl such as glycol diacrylate.

[Surfactant]
The surfactant used to obtain the binder resin when the toner particles constituting the toner are produced by suspension polymerization, miniemulsion polymerization aggregation or emulsion polymerization aggregation is not particularly limited. Are sulfonates (sodium dodecylbenzene sulfonate, sodium arylalkyl polyether sulfonates), sulfate esters (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, Ionic surfactants such as sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate, etc.) can be exemplified as suitable ones. Also, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester, etc. Nonionic surfactants can also be used. These surfactants are used as an emulsifier when a toner is obtained by an emulsion polymerization method, but may be used for other processes or purposes.

(Dispersion stabilizer)
When the toner particles constituting the toner are produced by suspension polymerization, a dispersion stabilizer made of an inorganic compound that can be easily removed can be used. Examples of the dispersion stabilizer include tricalcium phosphate, magnesium hydroxide, hydrophilic colloidal silica and the like, and tricalcium phosphate is particularly preferable. Since this dispersion stabilizer is easily decomposed by an acid such as hydrochloric acid, it can be easily removed from the surface of the toner particles.

(Polymerization initiator)
When the toner particles constituting the toner are produced by a suspension polymerization method, a miniemulsion polymerization aggregation method or an emulsion polymerization aggregation method, the binder resin can be polymerized using a radical polymerization initiator.

  In the case of using the suspension polymerization method, an oil-soluble radical polymerization initiator can be used. Examples of the oil-soluble radical polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2 '-Azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. Azo or diazo polymerization initiators, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4 -Dichlorobenzoyl peroxide, lauroyl peroxide , 2,2-bis- (4,4-t-butylperoxycyclohexyl) propane, peroxide-based polymerization initiators such as tris- (t-butylperoxy) triazine and polymers having a peroxide in the side chain An initiator etc. can be mentioned.

[Chain transfer agent]
For the purpose of adjusting the molecular weight of the binder resin when the toner particles constituting the toner are produced by suspension polymerization, miniemulsion polymerization aggregation or emulsion polymerization aggregation, a commonly used chain transfer agent is used. Can be used.

  The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as n-octyl mercaptan, n-decyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide. And α-methylstyrene dimer and the like are used.

[Colorant]
As the colorant constituting the toner, known inorganic or organic colorants can be used. Specific colorants are shown below.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite.

  The image forming method of the present invention can form a monochrome image or a color image.

  As a colorant for magenta or red when forming a color image, C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the colorant for orange or yellow when forming a color image include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, and the like.

  As a colorant for green or cyan when forming a color image, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  The above colorants can be used alone or in combination of two or more.

  The addition amount of the colorant is in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

  As the colorant, a surface-modified one can also be used. As the surface modifier, conventionally known ones can be used, and specifically, silane coupling agents, titanium coupling agents, aluminum coupling agents and the like can be preferably used.

〔Release agent〕
The toner particles constituting the toner may contain a release agent as necessary. Various known waxes can be used as the charge control agent.

  The addition amount of the release agent in the toner is preferably 1 to 30% by mass and more preferably 5 to 20% by mass with respect to the binder resin.

[Charge control agent]
The toner particles constituting the toner may contain a charge control agent as necessary. Various known compounds can be used as the charge control agent.

  In addition, inorganic fine particles can be added as an external additive.

  As materials constituting the inorganic fine particles, silica, alumina, titania, zirconia, magnesium hydroxide, calcium hydroxide, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, magnesium oxide, cerium oxide, zinc oxide, Examples thereof include chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, tellurium oxide, manganese oxide, boron oxide, silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, and boron nitride.

  Further, the inorganic fine particles may be subjected to a hydrophobic treatment. In the treatment for hydrophobization, it is preferable to perform a hydrophobizing treatment with a so-called coupling agent such as various titanium coupling agents and silane coupling agents, and further, a hydrophobizing treatment with a higher fatty acid metal salt is also preferably used. .

[Particle size of toner particles]
The toner particles preferably have a volume-based median diameter of 3 to 8 μm. This particle diameter can be controlled by adjusting the dispersion diameter of the oil droplets when toner particles are formed by suspension polymerization.

  When the volume-based median diameter is 3 to 8 μm, the reproducibility of fine lines and high image quality of photographic images can be achieved, and the amount of toner consumption can be reduced compared to the case of using a large particle size toner. be able to.

  The volume-based median diameter of the toner particles can be measured using a Coulter Multisizer III (manufactured by Beckman Coulter, Inc.) with a 50 μm aperture and a particle size distribution in the range of 1.0 to 40 μm.

  Measurement and calculation are performed using a device in which a computer system for data processing (manufactured by Beckman Coulter) is connected to "Coulter Multisizer 3" (manufactured by Beckman Coulter). As a measuring means, 0.02 g of toner was conditioned with 20 g of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant 10 times with pure water for the purpose of dispersing the toner). Thereafter, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measured concentration is 8% by mass. By setting this concentration range, a reproducible measurement value can be obtained. The measurement conditions are as follows: the measurement particle count is 25000, the aperture diameter is 50 μm, and the range of 1 to 40 μm, which is the measurement range, is divided into 256 to calculate each frequency value. The particle diameter of 50% from the larger volume integrated fraction is defined as the median diameter on the volume basis.

  The two-component developer comprising the toner of the present invention and a carrier can be adjusted by mixing the carrier of the present invention and the above-described toner. The toner concentration varies depending on development conditions and development methods, but is 3 to 15% by mass, preferably 4 to 10% by mass.

  As a developing method in which the two-component developer of the present invention can be used, any developing method in which a usual two-component developer can be used can be used without any problem. The gap between the photoreceptor and the developer may be 100 to 2000 μm, and may be contact development or non-contact development. The developing bias may be a system in which an AC bias is applied in addition to a DC electric field. Further, it can be used not only for monochrome development but also for a full-color image forming system using four primary colors of yellow, magenta, cyan and black.

[Image Forming Method and Image Forming Apparatus]
FIG. 1 is a schematic view of an image forming apparatus showing an example of an image forming method of the present invention.

  As shown in FIG. 1, the image forming apparatus 1 is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 9Y, 9M, 9C, and 9K, a belt-like intermediate transfer member 6 and a paper feed. And a toner cartridge 5Y, 5M, 5C, and 5K, a fixing device 10, an operation unit 91, and the like.

  An image forming unit 9Y for forming a yellow image includes a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a transfer unit 7Y, and a cleaning unit 8Y arranged around an image carrier (hereinafter referred to as a photoreceptor) 1Y. Have

  The image forming unit 9M that forms a magenta image includes a photoreceptor 1M, a charging unit 2M, an exposure unit 3M, a developing device 4M, a transfer unit 7M, and a cleaning unit 8M.

  The image forming unit 9C that forms a cyan image includes a photoreceptor 1C, a charging unit 2C, an exposure unit 3C, a developing device 4C, a transfer unit 7C, and a cleaning unit 8C.

  The image forming unit 9K that forms a black image includes a photoreceptor 1K, a charging unit 2K, an exposure unit 3K, a developing device 4K, a transfer unit 7K, and a cleaning unit 8K.

  The intermediate transfer body 6 is wound around a plurality of rollers 6A, 6B, and 6C and is rotatably supported.

  Each color image formed by the image forming units 9Y, 9M, 9C, and 9K is sequentially primary-transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K, and the combined color image. Is formed.

  The paper P (also referred to as transfer material, transfer paper, recording material, image support, etc., which is usually plain paper) P stored in a paper feed cassette 20 serving as paper feed means is fed one by one by a paper feed roller 21. The sheet is fed, conveyed to the transfer means 7A through the registration roller 22, and the color image is secondarily transferred onto the sheet P.

  The paper P on which the color image has been transferred is fixed by the fixing device 10 which is the fixing device of the present invention, and is sandwiched by the paper discharge roller 25 through the transport rollers 23 and 24 which are transport means, and is discharged outside the machine. It is placed on the paper tray 26.

  Hereinafter, the present invention will be described more specifically with reference to the following examples, but the present invention is not limited thereto.

[Production of carrier]
Using “Resin 1 and 2” shown in Table 1 below and “Silicone resin particles 1 to 7” shown in Table 2 below, “Invention Carriers 1 to 10” and “Comparative Carriers 1 to 5” are prepared by the following procedure. did.

(1) Production of “Invention Carrier 1” Table 1 shows 100 parts by mass of Mn—Mg ferrite particles having a volume average particle diameter of 50 μm and a saturation magnetization of 10.7 × 10 ⁻⁵ Wb · m / kg. 1.8 parts by mass of copolymer resin (resin 1) fine particles of methyl methacrylate / styrene (copolymerization ratio 50:50) and 2.2 parts by mass of silicone resin particles 1 having a number average primary particle diameter of 200 nm shown in Table 2 Part is put into a high-speed mixer equipped with stirring blades, stirred and mixed at 120 ° C. for 60 minutes, a resin layer is formed on the surface of the Mn—Mg ferrite particles by the action of mechanical impact force, and the present invention has a resin coating layer. Carrier 1 "was produced. The thickness of the resin coating layer of this “invention carrier 1” was 2540 nm.

(2) Production of “Invention Carriers 2-12” and “Comparative Carriers 1-5” As shown in Table 3 below instead of “silicone resin particles 1” used in the production of “invention carrier 1” “Invention carriers 2 to 5” and “comparative carriers 2 and 3” were prepared in the same procedure except that “silicone resin particles 2 to 7” were used. Further, in place of “Resin 1” used in the production of “Invention Carrier 1”, “Resin 2” is used as shown in Table 3 below, and in place of “Silicone resin particle 1” in Table 3 below. As shown, “invention carriers 6 to 10” were prepared in the same procedure except that “silicone resin particles 1 to 5” were used.

  Furthermore, “Comparative Carrier 1” was prepared in the same procedure except that “Silicone Resin Particle 1” was not added in the preparation of “Invention Carrier 1”. The “invention carriers 11 and 12” and the “comparative carriers 4 and 5” were prepared in the same procedure except for the changes shown in

  Table 3 shows the types and amounts of the resins and silicone resin particles used in “Invention Carriers 1-12” and “Comparative Carriers 1-5” prepared in the above procedure, carrier particle size, resin layer thickness, and swell. Show.

(Preparation of developer)
In accordance with the procedure shown below, a toner having a core-shell structure was prepared by an emulsion association method.

(1) Preparation of “Colorant Fine Particle Dispersion” 11.5 parts by mass of sodium n-dodecyl sulfate was added to 160 parts by mass of ion-exchanged water, and dissolved and stirred to prepare an aqueous surfactant solution. In this surfactant aqueous solution, 8 parts by mass of carbon black (Mogal L: manufactured by Cabot Corp.) is gradually added, and then dispersed using “Clearmix W Motion CLM-0.8 (MTechnic Co., Ltd.)”. Then, a “colorant fine particle dispersion” in which carbon black was dispersed in a number average primary particle size of 120 nm was prepared.

(2) Production of “core resin particle 1” The “core resin particle 1” having a multilayer structure was produced through first-stage polymerization, second-stage polymerization, and third-stage polymerization shown below.

(A) First-stage polymerization 4 parts by mass of an anionic surfactant shown below (Structural Formula 1) together with 3040 parts by mass of ion-exchanged water are charged into a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction device. Then, a surfactant aqueous solution was prepared.

(Structural Formula 1) C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ SO ₃ Na
A polymerization initiator solution in which 10 parts by mass of potassium persulfate (KPS) was dissolved in 400 parts by mass of ion-exchanged water was added to the surfactant aqueous solution, and the temperature was raised to 75 ° C. The resulting monomer mixture was dropped into the reaction vessel over 1 hour.

Styrene 532 parts by mass n-butyl acrylate 200 parts by mass Methacrylic acid 68 parts by mass n-octyl mercaptan 16.4 parts by mass After the above monomer mixture is added dropwise, the system is heated and stirred at 75 ° C. for 2 hours. Polymerization (first stage polymerization) was performed to prepare resin particles. This resin particle is referred to as “resin particle A1”. The “resin particle A1” produced by the first stage polymerization had a weight average molecular weight of 16,500.

(B) Second stage polymerization Into a flask equipped with a stirrer, a monomer mixed solution composed of the following compounds was charged, and subsequently 93.8 parts by mass of pentaerythritol tetrabehenyl ester was added as a release agent. The solution was heated to 90 ° C. and dissolved. In this way, a monomer solution was prepared.

Styrene 101.1 parts by weight n-butyl acrylate 62.2 parts by weight Methacrylic acid 12.3 parts by weight n-octyl mercaptan 1.75 parts by weight On the other hand, 3 parts by weight of the anionic surfactant is dissolved in 1560 parts by weight of ion-exchanged water. An aqueous surfactant solution was prepared and heated to 98 ° C. A mechanical system having a circulation path after adding 32.8 parts by mass (in terms of solid content) of the “resin particles A1” to the surfactant aqueous solution and further adding the monomer solution containing the paraffin wax. It was mixed and dispersed for 8 hours with a disperser “CLEAMIX (M Technique Co., Ltd.)”. An emulsified particle dispersion containing emulsified particles having a dispersed particle size of 340 nm was prepared by the mixing and dispersing.

  Next, a polymerization initiator solution in which 6 parts by mass of potassium persulfate is dissolved in 200 parts by mass of ion-exchanged water is added to the emulsified particle dispersion, and the system is polymerized by heating and stirring at 98 ° C. for 12 hours. (Second stage polymerization) was performed to prepare resin particles. This resin particle is referred to as “resin particle A2”. The “resin particle A2” produced by the second stage polymerization had a weight average molecular weight of 23,000.

(C) Third-stage polymerization A polymerization initiator solution in which 5.45 parts by mass of potassium persulfate is dissolved in 220 parts by mass of ion-exchanged water is added to the “resin particles A2” obtained by the second-stage polymerization. Under a temperature condition of 80 ° C., a monomer mixed solution composed of the following compounds was added dropwise over 1 hour.

Styrene 293.8 parts by mass n-butyl acrylate 154.1 parts by mass n-octyl mercaptan 7.08 parts by mass After completion of the dropwise addition, the mixture was heated and stirred for 2 hours to perform polymerization (third stage polymerization). It cooled to 28 degreeC and produced "resin particle 1 for core parts." Prepared by third stage polymerization. The “core part resin particles 1” had a weight average molecular weight of 26,800.

(3) Production of “resin particles for shell” Polymerization was carried out in the same manner except that the monomer mixture used in the first stage polymerization in the production of “resin particles for core 1” was changed to the following. Reaction and post-reaction treatment were performed to produce “shell resin particles 1”.

Styrene 624 parts by weight 2-ethylhexyl acrylate 120 parts by weight Methacrylic acid 56 parts by weight n-octyl mercaptan 16.4 parts by weight (4) Preparation of “toner” “Toner” was prepared by the following procedure.

(A) Formation of “core part 1” In a reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introducing device,
420.7 parts by mass of resin particles 1 for core part (solid content conversion)
900 parts by weight of ion-exchanged water 200 parts by weight of colorant particle dispersion (converted to solid content)
Was added and stirred. After adjusting the temperature in the reaction vessel to 30 ° C., a 5 mol / liter sodium hydroxide aqueous solution was added to adjust the pH to 8 to 11.

  Next, an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added at 30 ° C. over 10 minutes with stirring. After standing for 3 minutes, the heating was started, and the system was heated to 65 ° C. over 60 minutes to associate the particles. In this state, the particle size of the associated particles was measured using “Multisizer 3 (manufactured by Coulter)”. When the volume-based median diameter of the associated particles reached 5.5 μm, 40.2 parts by mass of sodium chloride was ion-exchanged. The association was stopped by adding an aqueous solution dissolved in 1000 parts by mass of water.

  After termination of the association, the core temperature 1 was prepared by continuing the fusion by heating and stirring for 1 hour at a liquid temperature of 70 ° C. as an aging treatment.

  The average circularity of the “core part 1” was measured by “FPIA2000 (manufactured by Sysmex Corporation)” and found to be 0.912.

(B) Formation of Shell Next, the dispersion liquid of “core part 1” is set to 65 ° C., and 96 parts by mass (in terms of solid content) of “resin particle 1 for shell” is added. An aqueous solution in which 2 parts by mass of the product was dissolved in 1000 parts by mass of ion-exchanged water was added over 10 minutes, and then the temperature was raised to 70 ° C. and stirring was performed for 1 hour. In this way, after the “shell resin particles 1” were fused to the surface of the “core part 1”, an aging treatment was performed at 75 ° C. for 20 minutes to form a shell.

  Thereafter, an aqueous solution in which 40.2 parts by mass of sodium chloride was dissolved in 1000 parts by mass of ion-exchanged water was added to stop shell formation. Further, the colored particles produced by cooling to 30 ° C. at a rate of 8 ° C./min are filtered, washed repeatedly with ion exchange water at 45 ° C., and then dried with hot air at 40 ° C. Colored particles having a shell (toner base particles before external addition treatment) were prepared.

(C) External addition treatment The following external additives were added to the produced colored particles, and external addition treatment was performed with a Henschel mixer (manufactured by Mitsui Miike Mining Co., Ltd.) to produce a toner.

Silica surface-treated with hexamethylsilazane (average primary particle size 12 nm)
0.6 parts by mass Titanium dioxide surface-treated with n-octylsilane (average primary particle size 24 nm)
0.8 parts by mass The external addition treatment by the Henschel mixer was performed under the conditions of a peripheral speed of the stirring blade of 35 m / second, a treatment temperature of 35 ° C., and a treatment time of 15 minutes.

  A “toner” was prepared by the above procedure.

(5) Preparation of Developer A developer was prepared by mixing the carrier and the toner with a V-type mixer so that the toner concentration was 6% by mass. Among these, what was prepared using "Invention Carriers 1-12" is "Examples 1-12", what was prepared using "Comparative Carriers 1-5" is "Comparative Examples 1-5" The image evaluation shown below was performed using these developers.

[Evaluation]
For image evaluation, use a multifunction machine “bizhub PRO 1050e (manufactured by Konica Minolta Business Technologies Co., Ltd.)” that employs a printed image electrophotographic method, and evaluate the image by outputting it to A4 size fine paper (64 g / m ² ). It was.

  Under a normal temperature and humidity environment (temperature 20 ° C., relative humidity 50% RH), an image with a pixel rate of 5% was printed on the A4 size fine paper up to 1.5 million sheets intermittently on 10 sheets. At the start and after 1.5 million sheets, an evaluation print consisting of a solid black image, a solid white image, and a resolution image was output to evaluate fog density, image density, and resolution (thin line reproducibility).

<Fog density>
The fog density was measured by measuring the density of paper on which nothing was printed using a reflection densitometer “RD-918” manufactured by Macbeth Co., Ltd., and taking this average value as the blank paper density.

  Next, the density measurement was carried out at 20 locations for the solid white image portion of the evaluation print output at the start and after 1.5 million sheets, and the value obtained by subtracting the blank paper density from this average value was taken as the fog density. A fog density of 0.005 or less was regarded as acceptable (practically acceptable range).

<Image density>
For the solid black image portion of the evaluation print output at the start and after 1.5 million sheets, the density at 20 locations was measured using a reflection densitometer “RD-918” manufactured by Macbeth, and this average value was used as the image density. . An image density of 1.30 or higher was regarded as acceptable (practically acceptable range).

<Resolution (fine line reproducibility)>
Resolution images (thin line images) on the evaluation print output at the start and after 1.5 million sheets, specifically 3 / mm, 4 / mm, 5 / mm, 6 / mm, 7 / mm These five types of fine line images were visually observed using a magnifying glass having a magnification of 10 times, and those that did not cause fading or swelling on the fine line were judged as non-defective products. 5 lines / mm or more were regarded as acceptable.

  The results are shown in Table 4.

  As shown in Table 4, “Examples 1 to 12” using “Invention Carriers 1 to 12” having the configuration of the present invention are 1.5 million images at the start of image density, fog density, and resolution. Later, there was little change. On the other hand, in “Comparative Examples 1 to 5” using “Comparative Carriers 1 to 5” that do not have the configuration of the present invention, the image density, fog density, and resolution fluctuate at the start and after 1.5 million sheets. Remarkably, it was impossible to produce a stable print.

1 is a schematic diagram of an image forming apparatus showing an example of an image forming method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 9Y, 9M, 9C, 9K Image forming unit 6 Intermediate transfer body 10 Fixing apparatus 20 Paper feed cassette 30 Low resistance fine particle 40 Inorganic fine particle P Transfer material

Claims (6)

In an electrostatic latent image developing carrier having a resin coating layer in which at least the magnetic particle surface is coated with a resin, the resin coating layer has a number average primary particle size of 200 to 5000 nm in a resin layer mainly composed of an acrylic resin. A carrier for developing an electrostatic latent image, comprising 5 to 60% by mass of silicone resin particles based on the total mass of the resin coating layer. 2. The electrostatic latent image developing carrier according to claim 1, wherein waviness having a height difference of 0.5 to 1.5 [mu] m is present on the surface of the resin coating layer. 3. The static electricity according to claim 1, wherein the electrostatic latent image developing carrier has a volume average particle diameter of 20 to 70 μm and an average film thickness of the coating layer of 1.5 to 4.0 μm. Carrier for developing electrostatic latent images. The electrostatic latent image developing carrier according to any one of claims 1 to 3, wherein the resin coating layer is produced by a dry coating method. In the two-component developer comprising at least a binder resin and a toner containing a colorant and a carrier, the carrier is a carrier for developing an electrostatic latent image having a resin coating layer in which at least the magnetic particle surface is coated with a resin, The resin coating layer contains 5 to 60% by mass of silicone resin particles having a number average primary particle system of 200 to 5000 nm based on the total mass of the resin coating layer in a resin layer mainly composed of an acrylic resin. Two-component developer characterized. An image forming method comprising developing an electrostatic latent image using the two-component developer according to claim 5.

Images