JP2014085410A - Carrier for electrostatic charge image development, electrostatic charge image developer, process cartridge, image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development having excellent image density stability.SOLUTION: A carrier for electrostatic charge image development includes core particles, a coating layer coating the core particles, and titanium oxide attached to the surface of the coating layer. The carrier is mixed with toner, and stirred in a developing unit with the processing speed of 180 mm/sec. in RH of 12% at 10°C according to predetermined conditions, so as to determine a Ti amount after being stirred for five minutes in the developing unit, a Ti amount before being stirred in the developing unit, and a Ti amount after removal of the coating layer. The adhesive strength F of the titanium oxide calculated on the basis of the Ti amounts is 0.4 or more and 1.0 or less; and a difference between the net strength of Ti before being stirred in the developing unit measured by fluorescent X-ray analysis and the net strength of Ti after the removal of the coating layer measured by fluorescent X-ray analysis is 0.01 or more and 0.30 or less.

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developer, a process cartridge, an image forming apparatus, and an image forming method.

  Conventionally, in electrophotography, an electrostatic charge image is formed on a latent image holding member (photosensitive member) or electrostatic recording member using various means, and electrostatic charge particles called toner are attached to the electrostatic charge image. Is used. In developing an electrostatic charge image, toner and carrier are mixed and triboelectrically charged to give an appropriate amount of positive or negative charge to the toner. Carriers are generally classified into a coated carrier having a coating layer on the surface and an uncoated carrier having no coating layer, and the coated carrier is excellent in consideration of the developer life and the like.

  Although there are various characteristics required for the coat carrier, it is required to impart an appropriate charge amount (charge amount or charge distribution) to the toner and maintain the charge amount over a long period of time. For this purpose, it is important not to change the chargeability of the toner even in response to environmental changes such as the impact resistance, friction resistance, temperature and humidity of the carrier, and various coated carriers have been proposed.

  For example, a copolymer of a nitrogen-containing fluorinated alkyl (meth) acrylate and a vinyl monomer or a copolymer of a fluorinated alkyl (meth) acrylate and a nitrogen-containing vinyl monomer is coated on the surface of the carrier core, It has been proposed to obtain a long-life coat carrier (see, for example, Patent Document 1 or Patent Document 2).

  For example, it has been proposed to improve the charging property when left standing by adding resin particles to the coating layer (see, for example, Patent Document 3).

JP 61-80161 A JP 61-80162 A Japanese Patent Laid-Open No. 11-231574

  An object of the present invention is to provide a carrier for developing an electrostatic image having excellent image density stability.

Specific means for achieving the above object are as follows.
That is, the invention according to claim 1
A core material particle, a coating layer covering the core material particle, and titanium oxide attached to the surface of the coating layer,
The process speed is 180 mm / sec. At 10 ° C. and 12% RH in the state of being mixed with toner according to the following condition A Based on the amount of Ti after stirring for 5 minutes in the developing unit, the amount of Ti before stirring in the developing unit, and the amount of Ti after removing the coating layer, the following formula (1) The adhesion strength F of the titanium oxide calculated from is 0.4 or more and 1.0 or less,
The difference between the net intensity of Ti by X-ray fluorescence analysis before stirring in the developing unit and the net intensity of Ti after X-ray fluorescence analysis after removing the coating layer is 0.01 or more and 0.30. The following electrostatic charge image developing carrier.

Condition A: 400 parts of the electrostatic charge image developing carrier and 24 parts of the toner are stirred for 30 minutes at 20 rpm under a condition of 24 ° C. and 55% RH with a container rotating V-type mixer.

The invention according to claim 2
An electrostatic charge image developer comprising the electrostatic charge image developing carrier according to claim 1 and an electrostatic charge image developing toner.

The invention according to claim 3
At least one selected from the group consisting of a latent image holder, a charging means for charging the surface of the latent image holder, and a cleaning means for removing toner remaining on the surface of the latent image holder;
A developing unit that stores the electrostatic charge image developer according to claim 2 and that develops the electrostatic charge image formed on the surface of the latent image holding body with the electrostatic charge image developer to form a toner image;
And a process cartridge that can be attached to and detached from the image forming apparatus.

The invention according to claim 4
The latent image holding member, a charging unit for charging the surface of the latent image holding member, an electrostatic charge image forming unit for forming an electrostatic charge image on the surface of the charged latent image holding member, and the electrostatic charge image. And developing means for forming a toner image by developing with the electrostatic charge image developer, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image to the recording medium. An image forming apparatus.

The invention according to claim 5
3. A charging step for charging the surface of the latent image holding member, an electrostatic charge image forming step for forming an electrostatic charge image on the surface of the charged latent image holding member, and the electrostatic charge image development according to claim 2. An image forming method comprising: a developing step for forming a toner image by developing with an agent; a transferring step for transferring the toner image to a recording medium; and a fixing step for fixing the toner image on the recording medium.

  According to the first aspect of the present invention, the adhesion strength F of titanium oxide is out of the range of 0.4 or more and 1.0 or less, or the difference in net intensity by the fluorescent X-ray analysis of Ti is 0.01 or more. An electrostatic charge image developing carrier having excellent image density stability is provided as compared with a case where it is outside the range of 0.30 or less.

  According to the second aspect of the present invention, the adhesion strength F of titanium oxide is outside the range of 0.4 or more and 1.0 or less, or the difference in net intensity by Ti X-ray fluorescence analysis is 0.01 or more. An electrostatic charge image developer excellent in stability of image density is provided as compared with a case where it is outside the range of 0.30 or less.

  According to the invention of claim 3, the adhesion strength F of titanium oxide is outside the range of 0.4 or more and 1.0 or less, or the difference in net intensity by Ti X-ray fluorescence analysis is 0.01 or more. Compared to a case where the value is outside the range of 0.30 or less, it is possible to easily handle the electrostatic image developer having excellent image density stability, and to improve the adaptability to various types of image forming apparatuses.

  According to the invention of claim 4, the adhesion strength F of titanium oxide is outside the range of 0.4 or more and 1.0 or less, or the difference in net intensity by the fluorescent X-ray analysis of Ti is 0.01 or more. There is provided an image forming apparatus using an electrostatic charge image developer that is excellent in stability of image density as compared with a case where it is outside the range of 0.30 or less.

  According to the fifth aspect of the present invention, the adhesion strength F of titanium oxide is outside the range of 0.4 or more and 1.0 or less, or the difference in net intensity by Ti X-ray fluorescence analysis is 0.01 or more. There is provided an image forming method using an electrostatic charge image developer which is excellent in stability of image density as compared with a case where it is outside the range of 0.30 or less.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment. It is a schematic block diagram which shows the image forming apparatus which concerns on 2nd embodiment. It is a schematic block diagram which shows an example of the process cartridge of this embodiment.

  Hereinafter, embodiments of the electrostatic charge image developing carrier, the electrostatic charge image developer, the process cartridge, the image forming apparatus, and the image forming method of the present invention will be described in detail.

<Carrier for developing electrostatic image>
The electrostatic image developing carrier of the present embodiment (hereinafter sometimes simply referred to as “carrier”) includes core material particles, a coating layer that coats the core material particles, and an oxidation film that adheres to the surface of the coating layer. And a process speed of 180 mm / sec. At 10 ° C. and 12% RH in a state of being mixed with toner according to the following condition A. Based on the amount of Ti after stirring for 5 minutes in the developing unit, the amount of Ti before stirring in the developing unit, and the amount of Ti after removing the coating layer, the following formula (1) The adhesion strength F of the titanium oxide calculated from the above is 0.4 or more and 1.0 or less, and the net strength by the fluorescent X-ray analysis of Ti before stirring in the developing device and the coating layer are removed. The difference between the Ti intensity and the net intensity by subsequent X-ray fluorescence X-ray analysis is 0.01 or more and 0.30 or less.

Condition A: 400 parts of the electrostatic image developing carrier and 24 parts of the toner are stirred for 30 minutes at 20 rpm under a condition of 24 ° C. and 55% RH using a container rotating V-type mixer.

Conventionally, TiO ₂ adhering to the carrier surface is likely to be detached due to stress in the developing device during continuous output in image formation by electrophotographic method, and the charge maintenance property of the carrier may be deteriorated. This makes it difficult to maintain stable charging when continuously outputting low-density images such as characters and high-density images such as photographs, and as a result, it may be difficult to stabilize the image density.

In this embodiment, by defining the adhesion strength F of titanium oxide (TiO ₂ ) adhering to the surface of the coating layer to 0.4 or more and 1.0 or less, even in the stress in the developing device at the time of continuous output, the carrier Desorption of TiO ₂ adhering to the surface is suppressed, and deterioration of charge retention of the carrier is suppressed. Thereby, the stability of the image density is improved.
The carrier of this embodiment is particularly excellent in image density stability when continuously outputting a low-density image such as characters and a high-density image such as a photograph.

As the use situation of electrophotography is diversified as in recent years, it may be required to continuously output a large number of images and alternately output images having greatly different densities. For example, a case where a high-density photographic image is output after a large number of low-density character images are output. In such an output, there is a problem that the image density is lowered when a high-density image is output. This is because a large stress is applied to the carrier by continuous output, and TiO ₂ adhering to the surface of the carrier is detached for the purpose of stabilizing the charge, so that it becomes difficult to give an appropriate charge amount to the toner. As a result, it is presumed that the charging stability is lowered, and it is impossible to cope with an output having a greatly different image density.
In the present embodiment, the desorption of TiO ₂ is suppressed and the charging is stabilized by setting the adhesion strength F of TiO ₂ adhered to the carrier surface to 0.4 to 1.0. When the adhesion strength F is less than 0.4, TiO ₂ tends to be detached from the carrier surface. As a result, a carrier having an excessively large charge amount is generated, and the toner to be developed may be reduced and the image density may be lowered. . Although the adhesion strength F does not exceed 1, it indicates that the closer to 1, the more difficult it is for the titanium oxide to be detached from the carrier surface, and there is a case where the charge imparting ability of the carrier to the toner decreases as described later.
In this embodiment, the adhesion strength F is 0.4 or more and 1.0 or less, preferably 0.5 or more and 0.9 or less, and more preferably 0.6 or more and 0.8 or less.

Specifically, the adhesion strength F in this embodiment was measured by the following method.
(1) 400 parts of the carrier and 24 parts of the toner are stirred for 30 minutes at 20 rpm under a condition of 24 ° C. and 55% RH using a container-rotating V-type mixer (Condition A). As a result, a developer (before stirring in the developing device) is obtained. As the toner to be mixed, a toner containing a styrene acrylic resin as a binder resin and a copper phthalocyanine colorant as a colorant is used.
(2) The developer obtained in (1) is subjected to 5 in a low temperature and low humidity (10 ° C., 12% RH) environment in a developer unit of DocuCentre Color 400 (manufactured by Fuji Xerox Co., Ltd., process speed is 180 mm / sec.). Stir for minutes. This gives a developer (after stirring in the developer).
(3) Place 10 g of the developer obtained in (1) and (2) in a stainless steel gauge with a 12 μm mesh net attached to the upper and lower lids of a cylindrical container having a diameter of 10 cm and a height of 5 cm. The toner and carrier are separated by blowing air from the toner. As a result, the carrier (hereinafter referred to as B carrier) before being stirred in the developing device from the developer obtained in (1) was stirred in the developing device from the developer obtained in (2). A later carrier (hereinafter referred to as A carrier) is obtained.
(4) On the other hand, 5 parts of carrier is dispersed in 100 parts of toluene (organic solvent) and stirred, and the coating layer is removed from the carrier to obtain a carrier from which the coating layer has been removed (hereinafter referred to as C carrier). .
(5) The amount of Ti (Net intensity) of the obtained A carrier, B carrier, and C carrier is quantified with fluorescent X-rays. Ti amount of carrier A is “Ti amount after being stirred in the developer”, Ti amount of carrier B is “Ti amount before being stirred in the developer”, and Ti amount of C carrier is “coating” It corresponds to “Ti amount after removing the layer”.
(6) F is calculated from the formula (1) based on the obtained amount of Ti (net strength).

The core material particles used in the present embodiment may contain Ti. Therefore, when the amount of Ti in the carrier is measured by fluorescent X-ray analysis, it may not be possible to determine whether Ti is derived from the core material particles or titanium oxide attached to the surface of the coating layer. Since the titanium oxide attached to the surface of the coating layer is removed by removing the coating layer from the carrier, the “Ti amount after removing the coating layer” in this embodiment is the Ti amount derived from the core material particles. Means.
Therefore, the denominator of the formula (1) “Ti amount before being stirred in the developing device−Ti amount after removing the coating layer” is applied to the surface of the carrier before being subjected to stress due to stirring in the developing device. It means the amount of Ti derived from TiO ₂ attached. On the other hand, the molecule of formula (1) “Ti amount after being stirred in the developing device−Ti amount after removing the coating layer” is applied to the surface of the carrier after receiving stress due to stirring in the developing device. It means the amount of Ti derived from TiO ₂ attached. Ratio of “Ti amount before stirring in developing unit−Ti amount after removing coating layer” and “Ti amount after stirring in developing unit−Ti amount after removing coating layer” , The ratio of TiO ₂ desorbed due to the influence of stirring in the developing device is obtained. This ratio means the adhesion strength of TiO ₂ .

Further, the difference between the net intensity of the Ti before X-ray fluorescence analysis in the developing device and the net intensity of the Ti after X-ray fluorescence analysis after removing the coating layer (hereinafter referred to as “Ti fluorescence X The “difference in net intensity by line analysis” is sometimes defined as the absolute amount of TiO ₂ adhering to the surface of the coating layer before the TiO ₂ comes off due to agitation stress in the developing device.
The amount of TiO ₂ adhering to exhibit the effect of stabilizing the charging needs to be 0.01 or more and 0.30 or less as a difference in net intensity by fluorescent X-ray analysis of Ti. In general, the carrier can impart an appropriate charge amount to the toner by stirring with the toner. On the other hand, if the stirring is further continued, the charge imparting ability decreases. By attaching TiO ₂ to the surface of the carrier, an initial charge amount or a charge amount corresponding to a change in the toner amount can be imparted, and it is considered that the charge imparting ability of the carrier is maintained by appropriately desorbing. When the difference in net intensity by Ti X-ray fluorescence analysis is smaller than 0.01, the charge imparting ability is reduced, and the image is partially high in image density, or conversely, when the difference is larger than 0.30, the charge amount is Since the amount is high, the toner development amount may be reduced, resulting in an image having a low image density.
In this embodiment, the difference in net intensity by X-ray fluorescence analysis of Ti is 0.01 or more and 0.30 or less, preferably 0.05 or more and 0.25 or less, and more preferably 0.1 or more and 0.2 or less. desirable.

  The coating resin used in the present embodiment is not particularly limited. For example, polyolefin resin such as polyethylene and polypropylene; polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polychlorinated resin. Polyvinyl or polyvinylidene resins such as vinyl, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer, styrene / acrylic acid copolymer; straight silicone resin composed of organosiloxane bond or a modified product thereof; Fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate; urea / formal Amino resins such as hydrin resins; and epoxy resins. Moreover, these may be used in combination as needed.

  The carrier of the present embodiment is a resin-coated carrier having core material particles and a coating layer that covers the core material particles. Examples of the core particles used here include magnetic metals such as iron, steel, nickel and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads.

Examples of the method for forming the coating layer on the surface of the core particle include a wet coating method and a dry coating method.
Examples of the wet coating method include an immersion method in which core material particles are immersed in a coating layer forming solution, a spray method in which the coating layer forming solution is sprayed onto the surface of the core material particles, and the core material particles are fluidized in a fluidized bed. Fluidized bed method in which the coating layer forming solution is sprayed in a state of being made into a state, and a kneader coater method in which the core material particles and the coating layer forming solution are mixed in a kneader coater to remove the solvent. The method is particularly suitable.
The coating resin solution used in the wet coating method includes a coating layer resin, coating layer particles, and other components used as necessary, and a solvent for dissolving or dispersing them. The solvent is not particularly limited as long as it dissolves the coating resin. Specifically, aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane Etc. are used.
Examples of the dry coating method include a method of forming a coating layer by heating a mixture of core material particles and a coating layer forming material in a dry state. Specifically, for example, without using a solvent, the core material particles and the coating layer forming material are mixed in a gas phase and heated and melted to form a coating layer.

  The film thickness of the coating layer in the carrier of the present embodiment is desirably 0.1 μm or more and 10 μm or less, and more desirably 0.3 μm or more and 5 μm or less. The average particle diameter of the core material particles of the carrier of the present embodiment is desirably 10 μm or more and 500 μm or less, and more desirably 30 μm or more and 150 μm or less.

  The volume average particle diameter of the carrier of this embodiment is preferably 15 μm or more and 510 μm or less.

  Further, resin particles or the like may be used in the carrier coating layer of this embodiment for the purpose of controlling charging. The resin particles are not particularly limited, but those having charge control imparting properties are preferable, and examples thereof include melamine resin particles, urea resin particles, urethane resin particles, polyester resin particles, and acrylic resin particles.

  In addition, a conductive material such as carbon black may be used in combination for the carrier coating layer of this embodiment for the purpose of controlling resistance. Other than carbon black, for example, metals such as gold, silver, copper, zinc oxide, tin oxide, barium sulfate, aluminum borate, tin oxide, tin oxide doped with antimony, tin-doped indium oxide, aluminum Examples include zinc oxide doped with metal, resin particles coated with metal, and the like.

The TiO ₂ attached to the surface of the coating layer in the carrier of the present embodiment is not particularly limited, and general TiO ₂ particles are used. A particle diameter of 5 nm or more and 500 nm or less is used. If necessary, it may be used together other resin particles or metal particles with TiO ₂ particles.

As a method of attaching the TiO ₂ in the coating layer surface, a carrier and TiO ₂ prior to depositing the TiO _2, for example, a method of stirring and mixing in a V-blender (a container rotating V type mixer), a Henschel mixer Examples of the method include stirring and mixing. When TiO ₂ is adhered to the surface of the coating layer by stirring and mixing with a V blender, the stirring condition is preferably 10 to 50 minutes at 5 to 40 rpm, and 20 to 40 minutes at 10 to 30 rpm. Is more desirable.
The adhesion strength F is adjusted by adjusting the stirring conditions. Specifically, the adhesion strength F tends to increase by increasing the number of rotations of stirring. The adhesion strength F tends to increase by increasing the stirring time.

The addition ratio of the carrier and TiO ₂ prior to depositing the TiO ₂ in the coating layer surface in the case of stirred and mixed in a V-blender, TiO the carrier 100 parts by weight of prior to depositing the TiO ₂ in the coating layer surface ₂ is preferably 0.001 to 0.50 parts by mass, more preferably 0.005 to 0.25 parts by mass, and particularly preferably 0.01 to 0.10 parts by mass.
By adjusting the addition ratio of the carrier and TiO ₂ , the difference in net intensity by the fluorescent X-ray analysis of Ti is adjusted. By increasing the addition ratio of TiO ₂ , there is a tendency that the difference in net intensity according to the fluorescent X-ray analysis of Ti increases.

In the present embodiment, sieving may be performed after TiO ₂ is attached to the surface of the coating layer. The coarseness of the sieve used for the sieving of the carrier is preferably 1.5 or more and 4.0 or less, more preferably 2.0 or more and 3.0 or less, when the volume average particle diameter of the carrier is 1. desirable. By setting the coarseness of the sieve to the above range, the adhesion strength F is adjusted to a desirable range in the present embodiment.
In addition, the volume average particle diameter of the carrier of this embodiment is measured using, for example, a laser diffraction / scattering type particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by Beckman-Coulter). For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size at 50% cumulative is taken as the volume average particle size.

<Electrostatic image developer>
The electrostatic image developer of the present embodiment (hereinafter sometimes simply referred to as “developer”) is the carrier of the present embodiment and the electrostatic image developing toner (hereinafter simply referred to as “toner”). Containing. The developer of this embodiment is prepared by mixing the carrier and toner of this embodiment at an appropriate blending ratio. The carrier content ((carrier) / (carrier + toner) × 100) is preferably in the range of 85% by mass to 99% by mass, more preferably in the range of 87% by mass to 98% by mass, and still more preferably 89%. The range is from mass% to 97 mass%.

Hereinafter, the toner used for the developer according to the exemplary embodiment will be described.
The toner according to the exemplary embodiment includes a binder resin and a colorant as main components. Binder resins used include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate; Α-methylene aliphatic monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.

  In particular, typical binder resins include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride. Examples include copolymers, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, and polyamide can be mentioned.

  The binder resin has a softening temperature of 70 ° C. or higher and 150 ° C. or lower, a glass transition temperature of 40 ° C. or higher and 70 ° C. or lower, a number average molecular weight of 2000 or higher and 50000 or lower, a weight average molecular weight of 8000 or higher and 150,000 or lower, and an acid value of 5 or higher. It is desirable that it is 30 or less and the hydroxyl value is in the range of 5 to 40.

  Typical toner colorants include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3.

The toner particles are produced, for example, by a kneading and pulverizing method in which a binder resin, a colorant, and if necessary, a release agent, a charge control agent and the like are kneaded, pulverized, and classified; particles obtained by a kneading and pulverizing method A method of changing the shape by mechanical impact force or thermal energy; a dispersion obtained by emulsifying and dispersing a binder resin; and a dispersion of a colorant and, if necessary, a release agent and a charge control agent Emulsion aggregation method in which toner particles are obtained by mixing, aggregating and heat-fusing to obtain toner particles; a dispersion monomer formed by emulsion polymerization of a binder resin polymerizable monomer, a colorant, and a release agent as required An emulsion polymerization aggregation method in which toner particles are obtained by mixing with a dispersion of a charge control agent, etc., and agglomerating and heat-fusing; a polymerizable monomer to obtain a binder resin, a colorant, and if necessary Suspension polymerization method in which a solution of a mold release agent, charge control agent, etc. is suspended in an aqueous solvent and polymerized; Agent, and a release agent, if necessary, a dissolution suspension method and a solution such as a charge control agent granulated suspended in an aqueous solvent; or the like is used.
Further, a manufacturing method may be performed in which the toner particles obtained by the above method are used as a core, and resin particles are further adhered and heat-fused to have a core-shell structure. Among these, the toner of the exemplary embodiment is desirably a toner obtained by an emulsion aggregation method or an emulsion polymerization aggregation method (emulsion aggregation toner) from the viewpoint of imparting a preferable charge amount to the toner.

  These toner particles may be added with a fluidizing agent such as silica, titania or alumina, or an external additive such as a cleaning aid or a transfer aid such as polystyrene particles, polymethylmethacrylate particles or polyvinylidene fluoride particles. Good. A toner is obtained by adding an external additive to the toner particles. In particular, hydrophobic silica having a primary average particle size of 5 nm to 30 nm is preferably used.

  Additives include ingredients such as salicylic acid metal salts, metal-containing azo compounds, charge control agents such as nigrosine and quaternary ammonium salts, and anti-offset agents such as low molecular weight polypropylene, low molecular weight polyethylene and high molecular alcohol. May be. In particular, a low molecular weight polypropylene having a weight average molecular weight of 500 or more and 5000 or less is desirable. The average particle size of the toner of the present embodiment is smaller than 30 μm, and preferably in the range of 4 μm to 20 μm.

The toner of this embodiment preferably has a shape factor SF1 of 110 or more and 145 or less, more preferably 115 or more and 140 or less, and even more preferably 120 or more and 135 or less. When the shape factor SF1 is 110 or more and 145 or less, an image having excellent resolution is formed.
The shape factor SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope image with an image analyzer, and is obtained as follows, for example. For measurement of the shape factor SF1, first, an optical microscope image of toner spread on a slide glass is taken into a Luzex image analyzer through a video camera, and SF1 of the following formula is calculated for 50 or more particles to obtain an average value. Can be obtained.

SF1 = (ML ² / A) × (π / 4) × 100
Here, ML is the absolute maximum length of the particle, and A is the projected area of the particle.

<Image Forming Apparatus, Image Forming Method, and Process Cartridge>
The image forming apparatus of the present embodiment includes a latent image holding member, a charging unit that charges the surface of the latent image holding member, and an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the charged latent image holding member. , Developing means for developing the electrostatic image with the electrostatic image developer of the present embodiment to form a toner image, transfer means for transferring the toner image to a recording medium, and fixing the toner image on the recording medium Fixing means. The image forming apparatus according to the present exemplary embodiment may include a cleaning unit or the like for removing toner remaining on the surface of the latent image holding member as necessary.

  In this image forming apparatus, for example, the part including the developing unit may have a cartridge structure (process cartridge) that can be attached to and detached from the main body of the image forming apparatus. The process cartridge includes a latent image holding body, At least one selected from the group consisting of charging means for charging the surface of the latent image holding member and cleaning means for removing toner remaining on the surface of the latent image holding member, and electrostatic image development according to the present embodiment A developing means for storing an agent and developing an electrostatic charge image formed on the surface of the latent image holding body with the electrostatic charge image developer to form a toner image, and is detachably attached to the image forming apparatus. A process cartridge of the form is preferably used.

  By the image forming apparatus of the present embodiment, a charging step for charging the surface of the latent image holding member, an electrostatic charge image forming step for forming an electrostatic charge image on the surface of the charged latent image holding member, and A development step of developing the electrostatic image developer of the embodiment to form a toner image; a transfer step of transferring the toner image to a recording medium; and a fixing step of fixing the toner image on the recording medium. The image forming method of this embodiment is performed.

Hereinafter, although an example of the image forming apparatus of this embodiment is shown, it is not necessarily limited to this.
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment. The image forming apparatus 301 includes a charging unit 310, an exposure unit 312, an electrophotographic photosensitive member 314 that is a latent image holding member, a developing unit 316, a transfer unit 318, a cleaning unit 320, and a fixing unit 322. .

  In the image forming apparatus 301, around the electrophotographic photosensitive member 314, a charging unit 310 that is a charging unit that charges the surface of the electrophotographic photosensitive member 314 and the charged electrophotographic photosensitive member 314 are exposed according to image information. An exposure unit 312 that is an electrostatic image forming unit that forms an electrostatic image, a developing unit 316 that is a developing unit that develops the electrostatic image with a developer to form a toner image, and the surface of the electrophotographic photoreceptor 314 The transfer unit 318 that is a transfer unit that transfers the toner image formed on the surface of the recording medium 324 and foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 after the transfer are removed to remove the toner image. A cleaning unit 320 which is a cleaning means for cleaning the surface of the substrate is arranged in this order. A fixing unit 322 that is a fixing unit that fixes the toner image transferred to the recording medium 324 is disposed on the side of the transfer unit 318.

  The operation of the image forming apparatus 301 of this embodiment will be described. First, the surface of the electrophotographic photosensitive member 314 is charged by the charging unit 310 (charging process). Next, light is applied to the surface of the electrophotographic photosensitive member 314 by the exposure unit 312, and the charged charge in the exposed part is removed, and an electrostatic image is formed according to image information (electrostatic image formation). Process). Thereafter, the electrostatic charge image is developed by the developing unit 316, and a toner image is formed on the surface of the electrophotographic photosensitive member 314 (development process). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 314 and using a laser beam as the exposure unit 312, the surface of the electrophotographic photoconductor 314 is negatively charged by the charging unit 310. Then, a digital latent image is formed in a dot shape by the laser beam light, and a toner is applied to a portion irradiated with the laser beam light by the developing unit 316 to be visualized. In this case, a negative bias is applied to the developing unit 316. Next, a recording medium 324 such as paper is superimposed on the toner image at the transfer unit 318, and a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324. 324 is transferred (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 322, and is fused and fixed to the recording medium 324 (fixing step). On the other hand, foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 without being transferred are removed by the cleaning unit 320 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the recording medium 324 such as paper by the transfer unit 318, but may be transferred via a transfer body such as an intermediate transfer body.

  Hereinafter, a charging unit, a latent image holding member, an electrostatic charge image forming unit (exposure unit), a developing unit, a transfer unit, a cleaning unit, and a fixing unit in the image forming apparatus 301 of FIG. 1 will be described.

(Charging means)
As the charging unit 310 serving as a charging unit, for example, a charger such as a corotron as shown in FIG. 1 is used, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 314 or may apply an alternating current superimposed thereon. For example, such a charging unit 310 charges the surface of the electrophotographic photosensitive member 314 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 314. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Latent image carrier)
The latent image holding member has a function of forming at least a latent image (electrostatic charge image). As the latent image holding member, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 314 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order, if necessary. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. It may be a single layer type photoreceptor included in the above layer, and is preferably a laminated type photoreceptor. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Static charge image forming means)
There is no particular limitation on the exposure unit 312 which is an electrostatic charge image forming unit (exposure unit). And optical system equipment that exposes the light.

(Development means)
The developing unit 316 that is a developing unit has a function of developing a latent image formed on the latent image holding member with a developer containing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-described function, and may be selected according to the purpose. For example, an electrostatic image developing toner is electrophotographic using a brush, a roller, or the like. A known developing device having a function of adhering to the photoreceptor 314 may be used. The electrophotographic photosensitive member 314 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 318 serving as a transfer unit, for example, as shown in FIG. 1, a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324, and the toner image is transferred to the recording medium 324 by electrostatic force. A transfer roll and a transfer roll pressing device using a conductive roll or a semiconductive roll that transfers directly in contact with the recording medium 324 may be used. A direct current may be applied to the transfer roll as a transfer current applied to the latent image holding member, or an alternating current may be applied in a superimposed manner. The transfer roll may be set based on the image area width to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. As a transfer method, a method of directly transferring to a recording medium 324 such as paper or a method of transferring to a recording medium 324 via an intermediate transfer member may be used.

  A known intermediate transfer member may be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, blend material of PC / PAT, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is desirable.

(Cleaning means)
As the cleaning unit 320 serving as a cleaning unit, a blade cleaning method, a brush cleaning method, a roll cleaning method, or the like may be selected as long as it cleans foreign matter such as residual toner on the latent image holding member. Absent.

(Fixing means)
The fixing unit 322 as a fixing unit (image fixing device) fixes a toner image transferred to the recording medium 324 by heating, pressing, or heating and pressing, and includes a fixing member.

(recoding media)
Examples of the recording medium 324 to which the toner image is transferred include plain paper, an OHP sheet, and the like used for electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, the surface of the recording medium is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are used. May be.

  Further, in combination with trickle development proposed in Japanese Examined Patent Publication No. 2-21591, stable image formation can be achieved for a long time.

  FIG. 2 is a schematic configuration diagram illustrating a four-tandem color image forming apparatus that is an image forming apparatus according to the second embodiment. The image forming apparatus shown in FIG. 2 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel at a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20 is provided by being wound around a driving roller 22 and a support roller 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other from the left to the right in the drawing. The vehicle travels in the direction toward the unit 10K. A force is applied to the support roller 24 in a direction away from the drive roller 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the both. Further, an intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the driving roller 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K has yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four colors of toner are supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first image that forms the yellow image disposed on the upstream side in the intermediate transfer belt traveling direction is formed. The unit 10Y will be described as a representative. Note that the second to fourth components are denoted by reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y) in the same parts as the first unit 10Y. Description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photosensitive member 1Y, a charging roller 2Y for charging the surface of the photosensitive member 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on the color-separated image signal to form an electrostatic charge image. An exposure device (electrostatic image forming means) 3 for forming, a developing device (developing means) 4Y for supplying the charged toner to the electrostatic image and developing the electrostatic image, and transferring the developed toner image onto the intermediate transfer belt 20 A primary transfer roller 5Y (primary transfer unit) that performs the transfer and a photoconductor cleaning device (cleaning unit) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer are sequentially arranged.
The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rollers 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging roller 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y in this way is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

In the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. .
From the viewpoint of development efficiency, image graininess, gradation reproducibility, and the like, a bias potential (development bias) in which an AC component is superimposed on a DC component may be applied to the developer holder. Specifically, when the developer holder DC applied voltage Vdc is −300 to −700 V, the developer holder AC voltage peak width Vp-p may be in the range of 0.5 to 2.0 kV.
The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer position, a primary transfer bias is applied to the primary transfer roller 5Y, and electrostatic force directed from the photoreceptor 1Y to the primary transfer roller 5Y is applied to the toner image. As a result, the toner image on the photoreceptor 1 </ b> Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 onto which the four color toner images have been transferred through the first to fourth units is arranged on the image transfer surface side of the intermediate transfer belt 20, the support roller 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roller (secondary transfer means) 26 is connected to a secondary transfer portion. On the other hand, a recording paper (recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roller 26 and the intermediate transfer belt 20 are pressed against each other via a supply mechanism, and the secondary transfer bias is supplied to the support roller. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P is applied to the toner image, and the transfer bias is applied to the intermediate transfer belt 20. The toner image is transferred onto the recording paper P. Note that the secondary transfer bias at this time is determined according to the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording paper P is fed to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (roll-type fixing means) 28, the toner image is heated, and the color-superposed toner image is melted to record the recording paper. Fixed onto P.

  Examples of the recording medium to which the toner image is transferred include plain paper and OHP sheet used for electrophotographic copying machines, printers, and the like.

The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.
The image forming apparatus exemplified above is configured to transfer the toner image onto the recording paper P via the intermediate transfer belt 20, but the present invention is not limited to this configuration, and the toner image is directly transferred from the photoconductor. It may be a structure that is transferred to a recording sheet.

FIG. 3 is a schematic configuration diagram showing a preferred example embodiment of a process cartridge containing the electrostatic charge image developer of this embodiment. The process cartridge 200 combines the developing device 111 with the photosensitive member 107, the charging roller 108, the photosensitive member cleaning device 113, the opening 118 for exposure, and the opening 117 for static elimination exposure using the mounting rail 116. , And integrated. In FIG. 2, reference numeral 300 indicates a recording medium.
The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device 112, a fixing device 115, and other components (not shown). It forms a forming apparatus.

  The process cartridge 200 shown in FIG. 3 includes a photosensitive member 107, a charging device 108, a developing device 111, a cleaning device 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. The devices may be selectively combined. In addition to the developing device 111, the process cartridge according to the present embodiment may include at least one selected from the group consisting of the photosensitive member 107, the charging device 108, and the cleaning device (cleaning means) 113.

  Next, the toner cartridge will be described. The toner cartridge is detachably attached to the image forming apparatus, and contains at least toner to be supplied to a developing unit provided in the image forming apparatus. The toner cartridge only needs to contain at least toner, and may contain developer, for example, depending on the mechanism of the image forming apparatus.

  2 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and the developing devices 4Y, 4M, 4C, and 4K are respectively the developing devices ( And a toner supply pipe (not shown). Further, when the toner stored in the toner cartridge becomes low, the toner cartridge is replaced.

  Hereinafter, although an Example and a comparative example are given and this embodiment is described in detail in detail, this embodiment is not limited to the following examples. Unless otherwise specified, “part” and “%” are based on mass.

(Manufacture of carrier 1)
Ferrite particles (Powdertech, F300, average particle size 50 μm): 100 parts Toluene: 15 parts Methyl methacrylate polymer (Soken Chemical, sample MMA lacquer, concentration 15%): 2.5 parts Resin particles ( Nippon catalyst, melamine resin particles, poster FS, average particle size 100 nm): 0.7 parts ・ Carbon black (Cabot Corporation, BPL): 0.3 parts The above components excluding ferrite particles are dispersed for 10 minutes with a homomixer and coated A layer forming solution was prepared, and this solution and ferrite particles were stirred for 30 minutes with a vacuum degassing kneader maintained at 60 ° C., and then the pressure was reduced at 5 kPa for 60 minutes to distill off the toluene to form a coating layer. A resin-coated core material was obtained.
Thereafter, 100 parts of the obtained resin-coated core material and 0.046 parts of TiO ₂ particles (Taika, TiO ₂ particles, average particle diameter of 15 nm) were mixed with a V blender (20 rpm / 25 minutes), and the opening was 106 μm. The carrier 1 was obtained by carrying out the treatment with a sieve and attaching TiO ₂ particles to the surface of the carrier. The carrier 1 thus obtained had an adhesion strength F of 0.7, and a difference in net strength by Ti X-ray fluorescence analysis was 0.15.
The volume average particle diameter of the carrier 1 was 51 μm.

(Manufacture of carrier 2)
Carrier 2 was produced in the same manner as carrier 1 except that 100 parts of resin-coated core material and 0.028 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 29 minutes with a V blender. The obtained carrier 2 had an adhesion strength F of 0.78, and a difference in net strength by Ti X-ray fluorescence analysis was 0.11.

(Manufacture of carrier 3)
A carrier 3 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.070 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 30 minutes with a V blender. The adhesion strength F of the obtained carrier 3 was 0.79, and the difference in net intensity by Ti X-ray fluorescence analysis was 0.19.

(Manufacture of carrier 4)
The carrier 4 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.029 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 20 minutes using a V blender. The resulting carrier 4 had an adhesion strength F of 0.62 and a difference in net strength of 0.11 according to Ti fluorescent X-ray analysis.

(Manufacture of carrier 5)
The carrier 5 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.071 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 20 minutes with a V blender. The adhesion strength F of the obtained carrier 5 was 0.79, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.19.

(Manufacture of carrier 6)
The carrier 6 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.026 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 29 minutes with a V blender. The obtained carrier 6 had an adhesion strength F of 0.78, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.098.

(Manufacture of carrier 7)
A carrier 7 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.029 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 32 minutes with a V blender. The resulting carrier 7 had an adhesion strength F of 0.82 and a difference in net strength of 0.11 according to the fluorescent X-ray analysis of Ti.

(Manufacture of carrier 8)
A carrier 8 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.064 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 32 minutes with a V blender. The carrier 8 thus obtained had an adhesion strength F of 0.82 and a difference in net strength of 0.18 according to the fluorescent X-ray analysis of Ti.

(Manufacture of carrier 9)
The carrier 9 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.10 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 29 minutes with a V blender. The adhesion strength F of the obtained carrier 9 was 0.78, and the difference in net strength by Ti X-ray fluorescence analysis was 0.22.

(Manufacture of carrier 10)
The carrier 10 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.10 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 20 minutes with a V blender. The carrier 10 thus obtained had an adhesion strength F of 0.62, and a difference in net strength by Ti X-ray fluorescence analysis was 0.22.

(Manufacture of carrier 11)
A carrier 11 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.064 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 18 minutes with a V blender. The obtained carrier 11 had an adhesion strength F of 0.58, and a difference in net strength by X-ray fluorescence analysis of Ti was 0.18.

(Manufacture of carrier 12)
The carrier 12 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.033 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 18 minutes with a V blender. The carrier 12 thus obtained had an adhesion strength F of 0.58, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.12.

(Manufacture of carrier 13)
A carrier 13 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.026 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 20 minutes with a V blender. The obtained carrier 13 had an adhesion strength F of 0.62, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.098.

(Manufacture of carrier 14)
A carrier 14 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.016 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 35 minutes with a V blender. The adhesion strength F of the obtained carrier 14 was 0.88, and the difference in net strength by Ti fluorescent X-ray analysis was 0.053.

(Manufacture of carrier 15)
A carrier 15 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.12 part of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 35 minutes with a V blender. The adhesion strength F of the obtained carrier 15 was 0.88, and the difference in net intensity by Ti fluorescent X-ray analysis was 0.24.

(Manufacture of carrier 16)
A carrier 16 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.12 part of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 15 minutes with a V blender. The obtained carrier 16 had an adhesion strength F of 0.52, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.24.

(Manufacture of carrier 17)
The carrier 17 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.016 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 15 minutes with a V blender. The adhesion strength F of the obtained carrier 17 was 0.52, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.053.

(Manufacture of carrier 18)
The carrier 18 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.014 part of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 35 minutes with a V blender. The adhesion strength F of the obtained carrier 18 was 0.88, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.046.

(Manufacture of carrier 19)
The carrier 19 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.016 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 38 minutes with a V blender. The adhesion strength F of the obtained carrier 19 was 0.93, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.053.

(Manufacture of carrier 20)
The carrier 20 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.12 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 38 minutes with a V blender. The obtained carrier 20 had an adhesion strength F of 0.93, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.24.

(Manufacture of carrier 21)
The carrier 21 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.16 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 35 minutes with a V blender. The adhesion strength F of the obtained carrier 21 was 0.88, and the difference in the net strength according to the fluorescent X-ray analysis of Ti was 0.26.

(Manufacture of carrier 22)
The carrier 22 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.16 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 16 minutes with a V blender. The carrier 22 thus obtained had an adhesion strength F of 0.52, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.26.

(Manufacture of carrier 23)
A carrier 23 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.16 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 12 minutes with a V blender. The adhesion strength F of the obtained carrier 23 was 0.47, and the difference in net strength by Ti fluorescent X-ray analysis was 0.26.

(Manufacture of carrier 24)
A carrier 24 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.016 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 13 minutes with a V blender. The adhesion strength F of the obtained carrier 24 was 0.48, and the difference in net strength by Ti fluorescent X-ray analysis was 0.053.

(Manufacture of carrier 25)
The carrier 25 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.014 part of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 15 minutes with a V blender. The adhesion strength F of the obtained carrier 25 was 0.53, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.046.

(Manufacture of carrier 26)
The carrier 26 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.01 part of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 40 minutes with a V blender. The adhesion strength F of the obtained carrier 26 was 0.97, and the difference in net intensity by Ti X-ray fluorescence analysis was 0.012.

(Manufacture of carrier 27)
A carrier 27 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.22 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 40 minutes with a V blender. The adhesion strength F of the obtained carrier 27 was 0.97, and the difference in net strength by fluorescent X-ray analysis of Ti was 0.29.

(Manufacture of carrier 28)
The carrier 28 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.22 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 9 minutes with a V blender. The obtained carrier 28 had an adhesion strength F of 0.42 and a difference in net strength by Ti X-ray fluorescence analysis of 0.29.

(Manufacture of carrier 29)
A carrier 29 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.01 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 9 minutes with a V blender. The obtained carrier 29 had an adhesion strength F of 0.42, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.012.

(Manufacture of carrier 30)
A carrier 30 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.0097 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 40 minutes with a V blender. The obtained carrier 30 had an adhesion strength F of 0.98, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.0097.

(Manufacture of carrier 31)
A carrier 31 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.27 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 40 minutes with a V blender. The adhesion strength F of the obtained carrier 31 was 0.97, and the difference in net intensity by fluorescent X-ray analysis of Ti was 0.31.

(Manufacture of carrier 32)
A carrier 32 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.27 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 9 minutes with a V blender. The obtained carrier 32 had an adhesion strength F of 0.42, and a difference in net strength by Ti X-ray fluorescence analysis was 0.31.

(Manufacture of carrier 33)
A carrier 33 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.29 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 7 minutes with a V blender. The adhesion strength F of the obtained carrier 33 was 0.38, and the difference in net strength by Ti X-ray fluorescence analysis was 0.29.

(Manufacture of carrier 34)
A carrier 34 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.01 parts of TiO ₂ particles were used, and the mixing condition was changed to 20 rpm / 7 minutes with a V blender. The obtained carrier 34 had an adhesion strength F of 0.38, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.012.

(Manufacture of carrier 35)
A carrier 35 was produced in the same manner as the carrier 1 except that 100 parts of the resin-coated core material and 0.0097 parts of TiO ₂ particles were used and the mixing condition was changed to 20 rpm / 9 minutes with a V blender. The obtained carrier 35 had an adhesion strength F of 0.42, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.0097.

(Manufacture of carrier 36)
Carrier 36 was obtained in the same manner as carrier 1 except that in the production of carrier 1, the coating layer was formed without adding resin particles. The obtained carrier 36 had an adhesion strength F of 0.7, and a difference in net strength by fluorescent X-ray analysis of Ti was 0.15.

(Manufacture of carrier 37)
Carrier 37 was obtained in the same manner as carrier 1 except that in the production of carrier 1, the coating layer was formed without adding carbon black. The obtained carrier 37 had an adhesion strength F of 0.7, and a difference in net strength by Ti X-ray fluorescence analysis was 0.15.

(Manufacture of toner)
-Preparation of Colorant Particle Dispersion 1-
Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd.): 50 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.): 5 parts Ion-exchanged water: 200 Part

  The above components were mixed, and dispersed for 5 minutes with an Ultra-Turrax manufactured by IKA, and further for 10 minutes with an ultrasonic bath to obtain a colorant particle dispersion 1 having a solid content of 21%. It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

-Preparation of release agent particle dispersion 1-
Paraffin wax: HNP-9 (Nippon Seiwa Co., Ltd.): 19 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.): 1 part Ion-exchanged water: 80 parts

  The above components were mixed in a heat-resistant container, heated to 90 ° C., and stirred for 30 minutes. Next, the molten liquid is circulated from the bottom of the container to the gorin homogenizer, and under a pressure condition of 5 MPa, a circulation operation corresponding to 3 passes is performed. Then, the pressure is increased to 35 MPa, and further a circulation operation corresponding to 3 passes is performed. It was. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent particle dispersion 1. It was 240 nm when the volume average particle diameter was measured with a particle size measuring instrument LA-700 manufactured by Horiba, Ltd.

-Preparation of resin particle dispersion 1-
<Oil layer>
-Styrene (Wako Pure Chemical Industries, Ltd.): 30 parts-N-butyl acrylate (Wako Pure Chemical Industries, Ltd.): 10 parts-β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.): 1.3 parts, dodecanethiol (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 parts <water layer 1>
-Ion-exchanged water: 17 parts-Anionic surfactant (DAWFAX 2A1, manufactured by Dow Chemical Co.): 0.4 parts <Aqueous layer 2>
・ Ion-exchanged water: 40 parts ・ Anionic surfactant (DAWFAX 2A1, manufactured by Dow Chemical Co.): 0.05 part ・ Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 part

  The above oil layer component and water layer 1 component were placed in a flask and mixed with stirring to obtain a monomer emulsified dispersion. The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The above monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. Polymerization was further continued at 75 ° C. after completion of the dropping, and the polymerization was terminated after 3 hours to obtain a resin particle dispersion 1.

(Preparation of Toner 1)
Resin particle dispersion 1: 150 parts Colorant particle dispersion 1: 30 parts Release agent particle dispersion 1: 40 parts Polyaluminum chloride: 0.4 parts

The above components were mixed and dispersed in a stainless steel flask using IKA Ultra Turrax, and then heated to 48 ° C. while stirring the flask in a heating oil bath. After holding at 48 ° C. for 80 minutes, 70 parts of the resin particle dispersion 1 was added thereto.
Then, after adjusting the pH in the system to 6.0 using an aqueous solution of sodium hydroxide having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, and solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed using 3,000 parts of ion exchange water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 5 times, and No. 1 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner particles.

To the toner particles, silica (SiO ₂ ) particles having a primary particle average particle diameter of 40 nm and subjected to a surface hydrophobization treatment with hexamethyldisilazane (hereinafter sometimes referred to as “HMDS”), metatitanic acid and isobutyltrimethoxysilane The metatitanic acid compound particles having an average primary particle diameter of 20 nm, which is the reaction product of the above, were added so that the coverage of the surface of the toner particles was 40% and mixed with a Henschel mixer to prepare toner 1.

(Preparation of developer and its evaluation)
100 parts of each of the carriers 1 to 37 and 6 parts of the toner 1 were mixed to prepare developers of Examples 1 to 31 and developers of Comparative Examples 1 to 6. Using these developers, an output test was performed with a modified machine of DocuCenter Color400 (Fuji Xerox Co., Ltd.). 10,000 sheets under high-temperature and high-humidity (30 ° C, 85% RH) environment, then 10,000 sheets under low-temperature and low-humidity (10 ° C, 12% RH) environment, low-density image (text image, toner loading) 5.0g / cm ² ) after outputting 10,000 sheets, a high-density image (photo image, toner loading 15.0 g / cm ² ) is output. The image quality was evaluated. When the image density unevenness is clearly visually confirmed with respect to the image output on the 20,000th sheet, △ when barely visually confirmed, △, when visual confirmation is not possible, but dirt is generated in the apparatus Was evaluated with ◎, and when it could not be confirmed visually, it was evaluated with ◎. The obtained results are shown in Table 1.

1Y, 1M, 1C, 1K, 107, 314 photoconductor (electrophotographic photoconductor)
2Y, 2M, 2C, 2K, 108, 310 Charging roller (charging unit)
3Y, 3M, 3C, 3K Laser beams 3, 312 Exposure device (exposure unit)
4Y, 4M, 4C, 4K, 111, 316 Development device (development unit)
5Y, 5M, 5C, 5K, 318 Primary transfer roller (transfer section)
6Y, 6M, 6C, 6K, 113, 320 Photoconductor cleaning device (cleaning unit)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Unit 20 Intermediate transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer rollers 28, 115, 322 Fixing device (fixing unit)
30 Intermediate transfer member cleaning device 112 Transfer device 116 Mounting rail 117 Opening 118 for static elimination exposure Opening 200 for exposure Process cartridge,
P, 300, 324 Recording paper (recording medium)

Claims (5)

A core material particle, a coating layer covering the core material particle, and titanium oxide attached to the surface of the coating layer,
The process speed is 180 mm / sec. At 10 ° C. and 12% RH in the state of being mixed with the toner according to the following condition A. Based on the amount of Ti after stirring for 5 minutes in the developing unit, the amount of Ti before stirring in the developing unit, and the amount of Ti after removing the coating layer, the following formula (1) The adhesion strength F of the titanium oxide calculated from is 0.4 or more and 1.0 or less,
The difference between the net intensity of Ti by X-ray fluorescence analysis before stirring in the developing unit and the net intensity of Ti after X-ray fluorescence analysis after removing the coating layer is 0.01 or more and 0.30. A carrier for developing an electrostatic image which is:

Condition A: 400 parts of the electrostatic image developing carrier and 24 parts of the toner are stirred for 30 minutes at 20 rpm under a condition of 24 ° C. and 55% RH using a container rotating V-type mixer.   An electrostatic charge image developer comprising the electrostatic charge image developing carrier according to claim 1 and an electrostatic charge image developing toner. At least one selected from the group consisting of a latent image holder, a charging means for charging the surface of the latent image holder, and a cleaning means for removing toner remaining on the surface of the latent image holder;
A developing unit that stores the electrostatic charge image developer according to claim 2 and that develops the electrostatic charge image formed on the surface of the latent image holding body with the electrostatic charge image developer to form a toner image;
And a process cartridge that is detachably attached to the image forming apparatus.   The latent image holding member, a charging unit for charging the surface of the latent image holding member, an electrostatic charge image forming unit for forming an electrostatic charge image on the surface of the charged latent image holding member, and the electrostatic charge image. And developing means for forming a toner image by developing with the electrostatic charge image developer, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image to the recording medium. Image forming apparatus.   3. A charging step for charging the surface of the latent image holding member, an electrostatic charge image forming step for forming an electrostatic charge image on the surface of the charged latent image holding member, and the electrostatic charge image development according to claim 2. An image forming method comprising: a developing step for developing a toner image by developing with an agent; a transferring step for transferring the toner image to a recording medium; and a fixing step for fixing the toner image on the recording medium.