JP2012168284A - Carrier for electrostatic charge development, developer for developing electrostatic charge image, process cartridge, image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge development capable of suppressing the occurrence of image unevenness.SOLUTION: There is provided a carrier for electrostatic charge development containing at least magnetic particles. An average interval Sm between protrusions and recesses on the surface of the magnetic particle satisfies the relation: 3.6 μm≤Sm≤8.0 μm and a maximum height Ry of the surface of the magnetic particle satisfies the relation: 0.5 μm≤Ry≤1.0 μm.

Description

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

In image formation by electrophotography, an electrostatic image is formed on a latent image carrier (photoreceptor) by a charging step and an exposure step (electrostatic image forming step), and developed in a developing step to form a toner image. The image is transferred onto a recording medium and fixed by heating or the like in a fixing step to obtain an image. The developer for developing an electrostatic image used in such an electrophotographic method includes a one-component developer using a toner in which a colorant is dispersed in a binder resin, and a two-component developer composed of a toner and a carrier. It is divided roughly into.
The two-component developer has a relatively large surface area so that it can be easily charged with toner, and by using magnetic particles for the carrier, it can be easily conveyed by a mag roll or the like. Widely used.

In order to provide a carrier for an electrophotographic developer suitable for obtaining a high quality image without causing carrier adhesion, at least a coat layer is provided on the surface of ferrite as a core material, and the following <Condition 1> to An electrophotographic developer carrier characterized by satisfying all <Condition 4> is disclosed (for example, see Patent Document 1).
<Condition 1> The volume-based variation coefficient K of the grain diameter satisfies the following formula [a].
5 ≦ K ≦ 30 ………… [a]
[However, K = (S / Dg) × 100, S is the standard deviation of the grain diameter, and Dg is the volume average diameter of the grain. ]
<Condition 2> The carrier magnetization σb at 1000 oersted of the carrier is 40 emu / g or more and 75 emu / g or less.
<Condition 3> The carrier has a weight average diameter (D4) of 25 μm or more and 65 μm or less, and particles of 12 μm or less are 0.3% by weight or less.
<Condition 4> The ratio “D4 / D1” of the weight average diameter (D4) and the number average diameter (D1) of the carrier is 1 or more and 1.3 or less.

Further, in order to provide a carrier powder used in an electrophotographic developer that has excellent magnetic properties and hardly damages the photoreceptor, the carrier powder is used in an electrophotographic developer and has a roundness of 0. 8 or more and 1.0 or less, and the specific surface area CS value when the particles are assumed to be spherical is 0.17 m ² / cc or more and 0.185 m ² / cc or less, and the surface roughness coefficient is 2.0 or more. A carrier powder for an electrophotographic developer, which is 2.5 or less, is disclosed (for example, see Patent Document 2).

Further, in order to prevent carrier adhesion and fogging and obtain a high-stability and high-quality copy image, the magnetic carrier particles containing at least a binder resin and magnetic metal oxide particles have a number average particle diameter Dn of the magnetic carrier particles. 5 μm or more and 25 μm or less, the specific resistance of the magnetic carrier particles is 5.0 × 10 ¹³ Ωcm or more when 25 V to 500 V is applied, and the true specific gravity of the magnetic carrier particles is 3.0 g / cm ³ or more and 4.9 g / cm ^3. The magnetic carrier particle has a magnetization strength at 1 kilo-Oersted of 100 emu / cm ³ or more and 300 emu / cm ³ or less, and the Fe (II) content relative to the eluted iron element concentration on the surface of the magnetic carrier particle is 0.001. A magnetic carrier characterized in that it is not less than 5.0% by weight and the magnetic carrier satisfies the following formula: (For example, refer to Patent Document 3).
−6.25R + 307 ≦ M ≦ −4.47R + 319
5 ≦ R ≦ 25
R: Number average particle diameter of magnetic carrier (μm)
M: Magnetization strength (emu / cm ³ ) at 1 kilo-Oersted of the magnetic carrier

JP 2006-033201 A JP 2007-272160 A Japanese Patent Laying-Open No. 2005-099072

  An object of the present invention is to provide an electrostatic charge developing carrier in which the occurrence of image unevenness is suppressed.

That is, the invention according to claim 1
Containing at least magnetic particles,
Electrostatic charge development in which the average interval Sm of the irregularities on the surface of the magnetic particles and the maximum height Ry of the surface of the magnetic particles are 3.6 μm ≦ Sm ≦ 8.0 μm and 0.5 μm ≦ Ry ≦ 1.0 μm For carriers.

The invention according to claim 2
2. The electrostatic charge developing carrier according to claim 1, wherein the arithmetic average roughness Ra of the surface of the magnetic particle is 0.1 μm ≦ Ra ≦ 0.5 μm.

The invention according to claim 3
The electrostatic charge developing carrier according to claim 1, further comprising a coating layer covering a surface of the magnetic particle.

The invention according to claim 4
The electrostatic image developing developer comprising: the electrostatic charge developing carrier according to any one of claims 1 to 3; and a toner having a volume average particle size distribution index GSDv of 1.15 to 1.21. It is an agent.

The invention according to claim 5
A process cartridge comprising at least a developer holder and containing the developer for developing an electrostatic image according to claim 4.

The invention according to claim 6
5. The latent image holding member, a charging unit that charges the surface of the latent image holding member, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge image according to claim 4. An image comprising: a developing unit that develops a toner image by developing with a developer for developing an electrostatic image; a transfer unit that transfers the toner image to a recording medium; and a fixing unit that fixes the toner image on the recording medium. Forming device.

The invention according to claim 7 provides:
5. The developer for developing an electrostatic charge image according to claim 4, wherein 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 latent image holding member, and the electrostatic charge image are developed. An image forming method comprising: a developing step for forming a toner image by developing the toner image; a transfer step for transferring the toner image to a recording medium; and a fixing step for fixing the toner image to the recording medium.

  According to the first aspect of the present invention, for electrostatic charge development in which the occurrence of image unevenness is suppressed as compared with the case where the average interval Sm of unevenness or the maximum height Ry of the surface of the magnetic particles is out of the above range. A career is provided.

  According to the invention which concerns on Claim 2, compared with the case where arithmetic mean roughness Ra of the surface of a magnetic particle remove | deviates from the said range, generation | occurrence | production of an image nonuniformity is further suppressed.

  According to the third aspect of the present invention, the occurrence of image unevenness is further suppressed as compared with the case where no coating layer is provided.

  According to the invention of claim 4, electrostatic charge image development in which the occurrence of image unevenness is suppressed as compared with the case where the average interval Sm of unevenness or the maximum height Ry of the magnetic particle surface is out of the above range. A developer is provided.

  According to the invention of claim 5, electrostatic charge image development in which the occurrence of image unevenness is suppressed as compared with the case where the average interval Sm of unevenness or the maximum height Ry of the magnetic particle surface is out of the above range. A process cartridge using the developer is provided.

  According to the invention of claim 6, the electrostatic charge image development in which the occurrence of image unevenness is suppressed as compared with the case where the average interval Sm of the unevenness or the maximum height Ry of the magnetic particle surface is out of the above range. An image forming apparatus using the developer is provided.

  According to the seventh aspect of the present invention, electrostatic charge image development in which the occurrence of image unevenness is suppressed as compared with the case where the average interval Sm of unevenness or the maximum height Ry of the magnetic particle surface is out of the above range. An image forming method using the developer is provided.

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

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

<Carrier for electrostatic charge development>
The electrostatic charge developing carrier according to the present embodiment (hereinafter sometimes referred to as the carrier of the present embodiment) contains at least magnetic particles, the average interval Sm of the irregularities on the surface of the magnetic particles, and the surface of the magnetic particles. The maximum height Ry of the carrier is 3.6 μm ≦ Sm ≦ 8.0 μm and 0.5 μm ≦ Ry ≦ 1.0 μm.

  When a print with a low image density such as text or a print with a large solid surface and a high image density is continuously performed, the image pattern is switched from a print with a low image density to a print with a high image density (or vice versa). The toner concentration of the developer may change greatly. When the toner density changes, the magnetic brush structure of the developing device may change, and image defects may occur. In particular, if the toner concentration suddenly becomes high when it is used at a low toner concentration, the developer is low in charge, but the printer's potential parameter is for high charge, and the toner develops excessively. It may be easy to be done. At this time, the toner density of the magnetic brush is high. If the uniformity of the magnetic brush is poor, the developed toner becomes non-uniform and image unevenness is likely to occur. Also, at low toner concentration, if the uniformity of the magnetic brush is poor, carrier scattering is likely to occur and white spots may occur in the image.

By using the carrier of this embodiment, the occurrence of image unevenness is suppressed. The reason is not clear, but it is presumed as follows.
In the carrier, when the surface of the core material (magnetic particles) is 3.6 μm ≦ Sm ≦ 8.0 μm and 0.5 μm ≦ Ry ≦ 1.0 μm, the grain boundaries of one magnetic particle are large. Since it is uniform, the variation in magnetization at the grain boundary is suppressed, and the variation in magnetization between grains in the magnetic particles and the variation in magnetization between magnetic particles are reduced. Therefore, the magnetic brush can be easily made uniform. Further, since the protrusions on the surface of the magnetic particles are small and uniform, even if the toner concentration of the developer composed of toner and carrier changes, the stirrability due to the protrusions and the flowability of the developer due to the small protrusions. Since the balance is suitable, the uniformity of the magnetic brush is maintained and the uneven distribution of toner is less likely to occur. As a result, it is assumed that the occurrence of image unevenness is suppressed.

Hereinafter, the components constituting the carrier of the present embodiment will be described.
The carrier of this embodiment contains at least the magnetic particles having the specific Sm value and Ry value, and may have a coating layer that covers the surface of the magnetic particles as necessary.

-Magnetic particles-
The average spacing Sm of the irregularities on the surface of the magnetic particles used in the present embodiment needs to be 3.6 μm ≦ Sm ≦ 8.0 μm, but is preferably 4.0 μm ≦ Sm ≦ 6.0 μm. If Sm is less than 3.6 μm, the grains are small and the variation in magnetization between grains tends to be large. At the same time, variations in magnetization between the magnetic particles are likely to occur, the magnetic brush becomes non-uniform, and image unevenness may occur. On the other hand, if Sm exceeds 8.0 μm, the grains are large and the number of protrusions on the surface of the magnetic particles is reduced, so that the stirability is insufficient with respect to the change in developer toner concentration, the magnetic brush becomes non-uniform, and image unevenness may occur. is there.
The maximum height Ry of the surface of the magnetic particles used in the present embodiment needs to be 0.5 μm ≦ Ry ≦ 1.0 μm, but preferably 0.6 μm ≦ Ry ≦ 0.9 μm. If Ry is less than 0.5 μm, the protrusions on the surface of the magnetic particles are small, so that the stirability is insufficient with respect to changes in the developer toner concentration, the magnetic brush becomes non-uniform, and image unevenness may occur. When Ry exceeds 1.0 μm, the protrusions on the surface of the magnetic particles are large, and the fluidity of the developer is deteriorated, which may cause a problem of image unevenness.

  In the present embodiment, the arithmetic average roughness Ra of the surface of the magnetic particles is preferably 0.1 μm ≦ Ra ≦ 0.5 μm, and more preferably 0.3 μm ≦ Ra ≦ 0.4 μm. When the Ra value is within the above range, the surface of the magnetic particles is smooth, and the magnetic brush uniformity with respect to the toner concentration is improved, so that uneven toner distribution in the mixed state of toner and carrier is less likely to occur. As a result, the occurrence of image unevenness is further suppressed.

The specific measurement method of the average spacing Sm, the maximum height Ry, and the arithmetic average roughness Ra on the surface of the magnetic particles is as follows. For 50 magnetic particles, an ultra-deep color 3D shape measurement microscope (VK-9500, Keyence) This is a method of obtaining the surface by observing the surface at a magnification of 3000 times.
The average interval Sm of the unevenness is obtained from a three-dimensional shape of the observed core surface, and a roughness curve is obtained, and an average value of the intervals between the valleys and the cycles obtained from the intersection where the roughness curve intersects the average line is obtained. The reference length for determining the Sm value is 10 μm, and the cutoff value is 0.08 mm.
For the maximum height Ry, a roughness curve is obtained, and a reference length is extracted in the direction of the average line. The height Yp from the average line of this extracted portion to the highest peak and the depth Yv to the lowest valley bottom The maximum height Ry is obtained by calculating the sum (Yp + Yv). The reference length for determining the Ry value is 10 μm, and the cutoff value is 0.08 mm.
The arithmetic average roughness Ra is obtained by obtaining a roughness curve, summing the measured value of the roughness curve and the absolute value of the deviation to the average line, and averaging them. The reference length for determining the Ra value is 10 μm, and the cutoff value is 0.08 mm.

  These Sm value, Ry value, and Ra value are measured according to JIS B 0601 (1994 version).

The magnetic particles used in the present embodiment are not particularly limited as long as they have the specific Sm value and Ry value described above, and are magnetic metals such as iron, steel, nickel and cobalt, or magnetic materials such as ferrite and magnetite. Examples thereof include an oxide, a magnetic particle-dispersed core material containing magnetic particles and a binder resin.
In the present embodiment, the magnetic particles may contain ferrite represented by the following formula (1).

(MO) _X (Fe ₂ O ₃ ) _Y formula (1)
In Formula (1), Y represents 2.1 or more and 2.4 or less, and X represents 3-Y. M represents a metal element, and contains at least Mn as the metal element.

  As M in the formula (1), Mn is mainly used, but at least one selected from the group consisting of Li, Ca, Sr, Sn, Cu, Zn, Ba, Mg, and Ti may be combined. However, it is desirable to select Li, Ca, Sr, Mg, and Ti from the environmental aspect.

  When producing magnetic particles, the sintering rate is adjusted by controlling the amount of Fe and the amount of Si as an additive, so the grain growth in the magnetic particles is controlled and the grain boundaries of the grains are large. It becomes uniform. Therefore, the Sm value, Ry value, and Ra value on the surface of the magnetic particles are controlled within the specific range.

During the sintering of the magnetic particles, the sintering of ferrite is controlled by adding SiO ₂ as an additive. The addition amount of SiO _2, the volume average particle size may be a SiO ₂ of 15nm or more 150nm or less was added in a volume ratio of the ferrite raw material 0.1% to 0.3% or less. By setting the addition amount of SiO _{2 in} the above range, ferrite becomes a desirable sintered state, and the Sm value, Ry value, and Ra value on the surface of the magnetic particles are controlled in the specific range.

In the present embodiment, the composition of ferrite contained in the magnetic particles and the molar ratio of Si to 1 mol of Fe contained in the magnetic particles are determined by the following method.
First, constituent elements can be identified by fluorescent X-rays. The content is measured using a calibration curve from quantitative analysis. The number of moles is obtained by dividing the obtained content by the atomic weight, and the mole ratio of Si to each Fe can be obtained from the ratio.

Although the manufacturing method of a magnetic particle is not specifically limited, For example, you may manufacture by passing through the following process.
An appropriate amount of each material constituting the magnetic particles is blended and pulverized with a bead mill or the like, and then heated to obtain an oxide (preliminary firing). Next, an appropriate amount of a dispersant, a binder resin such as polyvinyl alcohol is blended with the oxide, and pulverized / mixed for 8 hours to 35 hours with a wet ball mill or the like. The volume average particle diameter of the oxide after pulverization is 1 μm or more and 3 μm or less. At the time of pulverization / mixing, an Si component (such as SiO ₂ having a volume average particle diameter of 15 nm to 150 nm) is added as necessary. Next, granulation and drying are performed with a spray dryer or the like to prepare particles before firing. The final particle size is determined by the particle size at this time. Then, after baking at 1000 degreeC or more and 1300 degrees C or less, you may grind | pulverize and further classify | categorize into desired particle size distribution, and you may obtain a magnetic particle.
These manufacturing conditions differ depending on the additive material. Therefore, the target magnetic particles are produced by a combination of the composition of the additive material and the manufacturing conditions.

  In the present embodiment, the resin constituting the coating layer is not particularly limited as long as it is used as a matrix resin, and is selected according to the purpose. For example, polyolefin resins such as polyethylene and polypropylene; polyvinyl resins and polyvinylidene resins such as polystyrene, acrylic resins, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone Vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin composed of organosiloxane bond or modified product thereof; polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene, etc. Fluorine resin; Silicone resin; Polyester; Polyurethane; Polycarbonate; Phenol resin; Urea-formaldehyde resin, Melamine tree , Benzoguanamine resins, urea resins, amino resins such as polyamide resins, epoxy resins, per se known resins and the like. These may be used individually by 1 type and may use 2 or more types together.

The coating layer that coats the magnetic particles may contain conductive particles. Here, the conductivity means that the volume resistivity is less than 10 ⁷ Ω · cm.
Specific examples of the conductive particles include metal oxides such as carbon black, various metal powders, titanium oxide, tin oxide, magnetite, and ferrite. These may be used individually by 1 type and may use 2 or more types together. Among these, carbon black particles are desirable from the viewpoints of production stability, cost, conductivity, and the like. The type of carbon black is not particularly limited, but carbon black having a DBP oil absorption of about 50 ml / 100 g or more and 250 ml / 100 g or less is desirable because of its excellent production stability.

The method for forming the coating layer for coating the magnetic particles is not particularly limited. For example, the solvent includes conductive particles and a resin such as a styrene acrylic resin, a fluorine resin, or a silicone resin as a coating resin. Examples include a method using a coating layer forming solution.
Specifically, an immersion method in which magnetic particles are immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the magnetic particles, and the coating layer forming solution in a state where the magnetic particles are suspended by flowing air. And kneader coating method in which the solvent is removed. Among these, in this embodiment, the solution in which the coating resin is dissolved is stirred and dispersed using a disperser such as UltraTurrax T50, and the coating layer forming solution and magnetic particles are mixed in a kneader coater, Next, a kneader coating method for removing the solvent is desirable.

  The solvent used in the coating layer forming solution is not particularly limited as long as it dissolves the resin as a matrix resin, and can be selected from known solvents such as toluene and xylene. Aromatic hydrocarbons, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and the like.

  The carrier of this embodiment preferably has a volume average particle size of 30 μm to 90 μm, and more preferably 40 μm to 80 μm. If the volume average particle size is 30 μm or more, the carrier hardly adheres to the photoconductor, and if it is 90 μm or less, the deterioration of the image quality is suppressed.

  When the carrier of this embodiment has a coating layer, the average thickness of the coating layer is desirably 0.5 μm or more and 2.5 μm or less, and more desirably 1.0 μm or more and 2 μm or less.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image of the present embodiment (hereinafter sometimes referred to as the developer of the present embodiment) is configured as a two-component developer including the carrier and toner of the present embodiment.
Hereinafter, the toner used for the developer according to the exemplary embodiment will be described.

  The toner used in the exemplary embodiment may include, for example, toner particles including a colorant, a binder resin, a release agent, and the like, and an external additive.

  The toner particles used in the present embodiment may contain a binder resin, and the type of the binder resin is not particularly limited.

  Binder resins include ethylene resins such as polyethylene and polypropylene, styrene resins mainly composed of polystyrene, poly (α-methylstyrene), polymethyl methacrylate, polyacrylonitrile and the like (meth). Examples thereof include acrylic resins, polyamide resins, polycarbonate resins, polyether resins, polyester resins, and copolymer resins thereof. From the viewpoint of charging stability and development durability when used as an electrophotographic toner, styrene resins, ( A meth) acrylic resin, a styrene- (meth) acrylic copolymer resin and a polyester resin are preferred.

Styrene resins and (meth) acrylic resins, particularly styrene- (meth) acrylic copolymer resins are useful as binder resins in the present invention.
60 to 90 parts by mass of vinyl aromatic monomer (styrene monomer), 10 to 40 parts by mass of ethylenically unsaturated carboxylic acid ester monomer ((meth) acrylic acid ester monomer) A latex obtained by dispersing and stabilizing a copolymer obtained by polymerizing a monomer mixture composed of 1 part by mass or more and 3 parts by mass or less of an ethylenically unsaturated acid monomer with a surfactant. Can be preferably used.
The glass transition temperature of the copolymer is preferably 50 ° C. or higher and 70 ° C. or lower.

Below, the polymerizable monomer which comprises said copolymer resin is demonstrated.
Examples of styrene monomers include styrene, α-methyl styrene, vinyl naphthalene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene, 2-ethyl styrene, 3-ethyl styrene, 4-ethyl styrene, and the like. Examples include alkyl-substituted styrene having an alkyl chain, halogen-substituted styrene such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene, and fluorine-substituted styrene such as 4-fluorostyrene and 2,5-difluorostyrene. Styrene is preferred as the styrene monomer.

  Examples of the (meth) acrylate monomer include n-methyl (meth) acrylate, n-ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, ( N-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-decyl (meth) acrylate, n (meth) acrylate -Dodecyl, n-lauryl (meth) acrylate, n-tetradecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acryl Isobutyl acid, t-butyl (meth) acrylate, isopentyl (meth) acrylate, amyl (meth) acrylate, (meth) acrylic acid Pentyl, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, phenyl (meth) acrylate, biphenyl (meth) acrylate, (meth) acryl Diphenylethyl acid, t-butylphenyl (meth) acrylate, terphenyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth ) Diethylaminoethyl acrylate, methoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, β-carboxyethyl (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide and the like. As the (meth) acrylic acid ester monomer, n-butyl acrylate is preferable.

  A chain transfer agent can be used for the binder resin during the polymerization. Although there is no restriction | limiting in particular as a chain transfer agent, The compound which has a thiol component can be used. Specifically, alkyl mercaptans such as hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan are preferred, and in particular, the molecular weight distribution is narrow, so that the storage stability of toner at high temperatures is improved. preferable.

A crosslinking agent may be added to the binder resin as necessary. The cross-linking agent is typically a polyfunctional monomer having two or more ethylenically polymerizable unsaturated groups in the molecule.
Specific examples of such crosslinking agents include aromatic polyvinyl compounds such as divinylbenzene and divinylnaphthalene; divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl homophthalate, divinyl trimesate / trivinyl, and naphthalene dicarboxylic acid. Polyvinyl esters of aromatic polyvalent carboxylic acids such as divinyl acid and diphenyl biphenyl carboxylate; Divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridine dicarboxylate; Vinyl pyromutate, vinyl furan carboxylate, pyrrole-2- Vinyl esters of unsaturated heterocyclic compounds such as vinyl carboxylate and vinyl thiophenecarboxylate; butanediol methacrylate, hexanediol acrylate, octanediol methacrylate, decanediol acrylate (Meth) acrylic acid esters of linear polyhydric alcohols such as dodecanediol methacrylate; branches such as neopentylglycol dimethacrylate and 2-hydroxy-1,3-diacryloxypropane; ) Acrylic acid esters; Polyethylene glycol di (meth) acrylate, Polypropylene polyethylene glycol di (meth) acrylates; Divinyl succinate, divinyl fumarate, vinyl / divinyl maleate, divinyl diglycolate, vinyl / divinyl itaconate, acetone Divinyl dicarboxylate, divinyl glutarate, divinyl 3,3′-thiodipropionate, trans-aconite divinyl / trivinyl, divinyl adipate, divinyl pimelate, divinyl suberate, dibi azelate Le, sebacate, divinyl dodecanedioate divinyl, the polyvinyl esters of polycarboxylic acids such as oxalic acid divinyl and the like.
The content of the crosslinking agent is preferably in the range of 0.05% by mass or more and 5% by mass or less, more preferably in the range of 0.1% by mass or more and 1.0% by mass or less of the total amount of the polymerizable monomers.

  If the weight average molecular weight (Mw) of the binder resin is 6,000 or more, the occurrence of uneven fixing caused by the penetration of toner into the surface of a recording medium such as paper at the time of fixing is suppressed, or the fixed image Strength against bending resistance is improved. In addition, when the weight average molecular weight (Mw) is 35,000 or less, the viscosity at the time of melting does not become excessively high, so that the temperature for reaching a viscosity suitable for fixing does not increase, and as a result, low temperature fixability is achieved. can get.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC was performed with a THF solvent using a Tosoh column / TSKgel Super HM-M (15 cm) using a Tosoh GPC / HLC-8120 as a measuring device. The weight average molecular weight and the number average molecular weight are calculated using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from this measurement result.

The toner particles according to this embodiment may include a colorant. The colorant used in this embodiment may be a dye or a pigment, but a pigment is desirable from the viewpoint of light resistance and water resistance.
Desirable colorants include carbon black, aniline black, 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 Quinacridone, benzicine yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 185, C.I. I. Pigment red 238, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. A known pigment such as CI Pigment Blue 15: 3 may be used.

  The content of the colorant in the toner particles according to the exemplary embodiment is desirably in the range of 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the binder resin. It is also effective to use a surface-treated colorant or a pigment dispersant as necessary. By selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

The toner particles used in this embodiment may include inorganic particles.
The inorganic particles are added for various purposes, but may be added for adjusting the viscoelasticity of the toner. By adjusting the viscoelasticity, image glossiness and penetration into paper are adjusted. As the inorganic particles, known inorganic particles such as silica particles, titanium oxide particles, alumina particles, cerium oxide particles, or those obtained by hydrophobizing the surface thereof may be used alone or in combination of two or more. From the viewpoint of not impairing transparency such as color developability and OHP permeability, silica particles having a refractive index smaller than that of the binder resin are desirable. Further, the silica particles may be subjected to various surface treatments, and for example, those treated with a silane coupling agent, a titanium coupling agent, a silicone oil, or the like may be used.

In addition to the above components, various components such as a release agent, an internal additive, a charge control agent, and organic particles may be further added to the toner particles used in the exemplary embodiment as necessary.
Examples of the internal additive include metals such as ferrite, magnetite, reduced iron, cobalt, nickel, and manganese, alloys, and magnetic materials such as compounds containing these metals.

  Examples of the release agent include paraffin wax such as low molecular weight polypropylene and low molecular weight polyethylene; silicone resin; rosins; rice wax; carnauba wax; The melting temperature of these release agents is preferably 50 ° C. or higher and 100 ° C. or lower, and more preferably 60 ° C. or higher and 95 ° C. or lower. The content of the release agent in the toner is desirably 0.5% by mass or more and 15% by mass or less, and more desirably 1.0% by mass or more and 12% by mass or less. When the content of the release agent is 0.5% by mass or more, the occurrence of peeling failure is suppressed particularly in oilless fixing. When the content of the release agent is 15% by mass or less, the image quality and the reliability of image formation are improved, for example, the fluidity of the toner is improved.

  Known charge control agents may be used, but azo metal complex compounds, metal complex compounds of salicylic acid, and resin type charge control agents containing polar groups may be used.

The toner used in this embodiment may contain an external additive.
Examples of the external additive include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, and chloride. Examples include cerium, bengara, chromium oxide, cerium oxide, antimony trioxide, magnesium oxide, zirconium oxide, silicon carbide, and silicon nitride. Among these, silica particles and / or titania particles are desirable, and silica particles and titania particles subjected to hydrophobic treatment are particularly desirable.

The external additive is generally used for the purpose of improving the fluidity of the toner. Among external additives, by using TiO (OH) ₂ metatitanate, excellent transparency, good chargeability, environmental stability, fluidity, caking resistance, stable negative chargeability, stable image quality maintainability Is obtained. In addition, the hydrophobized compound of metatitanic acid has an electric resistance of 10 ¹⁰ Ω · cm or more, so that even if the transfer electric field is increased, high transferability can be obtained without generating a reversely charged toner. desirable. The volume average particle size of the external additive for the purpose of imparting fluidity is preferably in the range of 1 nm to 40 nm in terms of the primary particle size, and more preferably in the range of 5 nm to 20 nm. The volume average particle size of the external additive for the purpose of improving transferability is desirably 50 nm or more and 500 nm or less. These external additive particles are preferably subjected to surface modification such as hydrophobization in order to stabilize the chargeability and developability.

  A conventionally known method is used as the means for surface modification. Specific examples include coupling treatments such as silane, titanate, and aluminate. The coupling agent used for the coupling treatment is not particularly limited. For example, methyltrimethoxysilane, phenyltrimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, vinyltrimethoxysilane, γ-aminopropyltrimethoxysilane , Γ-chloropropyltrimethoxysilane, γ-bromopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, fluoroalkyltrimethoxysilane, hexa Silane coupling agents such as methyldisilazane; titanate coupling agents; aluminate coupling agents;

  Furthermore, various additives may be added as necessary. Examples of these additives include other fluidizing agents, cleaning aids such as polystyrene particles, polymethyl methacrylate particles, and polyvinylidene fluoride particles, and zinc stearyl. Examples thereof include abrasives for the purpose of removing adhering substances such as amide and strontium titanate.

  The addition amount of the external additive is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.3 to 2 parts by mass with respect to 100 parts by mass of the toner particles. When the addition amount is 0.1 parts by mass or more, there is an advantage that the fluidity of the toner is not deteriorated and the charging property and the charge exchange property are further improved. On the other hand, if the added amount is 5 parts by mass or less, the overcoating state is not caused, and a secondary failure that occurs when the excess inorganic oxide moves to the contact member is prevented.

  The method for producing the toner used in the exemplary embodiment is not particularly limited, and the toner is produced by a known dry method such as a kneading / pulverizing method or a wet method such as an emulsion aggregation method or a suspension polymerization method. Among these methods, an emulsion aggregation method that can easily produce a toner having a core-shell structure is desirable. Hereinafter, a method for producing a toner by the emulsion aggregation method will be described in detail.

In the emulsification aggregation method in this embodiment, the aggregation resin is formed by adding an aggregating agent to a mixed dispersion obtained by mixing at least a binder resin particle dispersion in which binder resin particles are dispersed and a colorant dispersion in which a colorant is dispersed. An agglomerated particle forming step, and the binder resin particle dispersion is further added to the mixed dispersion in which the agglomerated particles are formed, and the binder resin particles are adhered to the surface of the agglomerated particles to agglomerate the resin. You may have the adhesion process which forms particle | grains, and the fusion process which fuse | melts the said resin adhesion aggregation particle | grains by heating.
Since the toner particles produced through the above steps are covered with a shell layer composed of a binder resin, the colorant contained in the toner particles, the release agent used as necessary, etc. It is hard to be exposed to. For this reason, a toner containing toner particles produced through emulsion aggregation is preferable for suppressing fog because the charge is unlikely to decrease.

(Emulsification process)
The binder resin particle dispersion can be prepared by using a general polymerization method, such as emulsion polymerization, suspension polymerization, or dispersion polymerization. In addition, an aqueous medium and binder resin can be mixed. You may carry out by giving a shearing force to the obtained solution with a disperser. At that time, particles may be formed by heating to lower the viscosity of the binder resin component. Further, a dispersant may be used for stabilizing the dispersed binder resin particles. Furthermore, if the binder resin is oily and dissolves in a solvent having a relatively low solubility in water, the resin is dissolved in those solvents and dispersed in water together with a dispersant and a polymer electrolyte, and then heated or heated. A binder resin particle dispersion is prepared by evaporating the solvent under reduced pressure.

Examples of the aqueous medium include water such as distilled water and ion-exchanged water; alcohols; and the like.
Examples of the dispersant used in the emulsification step include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, and sodium polymethacrylate; sodium dodecylbenzenesulfonate; Anionic surfactants such as sodium octadecyl sulfate, sodium oleate, sodium laurate, potassium stearate, cationic surfactants such as laurylamine acetate, stearylamine acetate, lauryltrimethylammonium chloride, amphoteric such as lauryldimethylamine oxide Ionic surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene Surfactants such as nonionic surfactants such as alkyl amines; and the like are; tricalcium phosphate, aluminum hydroxide, calcium sulfate, calcium carbonate, inorganic salts such as barium carbonate.

  Examples of the disperser used for producing the binder resin particle dispersion include a homogenizer, a homomixer, a pressure kneader, an extruder, and a media disperser. As the size of the resin particles, the average particle size (volume average particle size) is preferably 1.0 μm or less, more preferably in the range of 60 nm to 300 nm, and even more preferably in the range of 150 nm to 250 nm. . If it is 60 nm or more, the resin particles become unstable particles in the dispersion, and therefore the aggregation of the resin particles becomes easy. If the particle size is 1.0 μm or less, the particle size distribution of the toner becomes narrow.

  In preparing the release agent dispersion, the release agent is dispersed in water together with an ionic surfactant, a polymer electrolyte such as a polymer acid or a polymer base, and then heated to a temperature equal to or higher than the melting temperature of the release agent. Dispersion treatment is performed using a homogenizer or a pressure discharge type disperser to which a strong shearing force is applied while heating. By undergoing such treatment, a release agent dispersion is obtained. During the dispersion treatment, an inorganic compound such as polyaluminum chloride may be added to the dispersion. Examples of desirable inorganic compounds include polyaluminum chloride, aluminum sulfate, highly basic polyaluminum chloride (BAC), polyaluminum hydroxide, and aluminum chloride. Among these, polyaluminum chloride and aluminum sulfate are desirable. The release agent dispersion is used in the emulsion aggregation method, but the release agent dispersion may also be used when the toner is produced by suspension polymerization.

By the dispersion treatment, a release agent dispersion liquid containing release agent particles having a volume average particle diameter of 1 μm or less is obtained. The more desirable volume average particle size of the release agent particles is 100 nm or more and 500 nm or less.
If the volume average particle size is 100 nm or more, the properties of the binder resin used are affected, but the release agent component is generally easily taken into the toner. In the case of 500 nm or less, the state of dispersion of the release agent in the toner is good.

  For the preparation of the colorant dispersion, a known dispersion method can be used. For example, a general dispersion means such as a rotary shear type homogenizer, a ball mill having a medium, a sand mill, a dyno mill, or an optimizer can be employed. Is not to be done. The colorant is dispersed in water together with a polymer electrolyte such as an ionic surfactant, a polymer acid, or a polymer base. The volume average particle diameter of the dispersed colorant particles may be 1 μm or less, but if it is in the range of 80 nm or more and 500 nm or less, the dispersion of the colorant in the toner is preferable without impairing the cohesiveness.

(Aggregated particle forming step)
In the aggregated particle forming step, a binder resin particle dispersion, a colorant dispersion, a release agent dispersion, and the like are mixed to form a mixed dispersion, and an aggregate is added to aggregate to form aggregated particles. In this case, the mixed dispersion may be heated at a temperature not higher than the glass transition temperature of the binder resin particles. Aggregated particles are often formed by making the pH of the mixed solution acidic under stirring. The pH is preferably in the range of 2 to 7.
In the agglomerated particle forming step, the release agent dispersion may be added and mixed at the same time with various dispersions such as a binder resin particle dispersion, or may be added in multiple portions.

  As the aggregating agent, a surfactant having a polarity opposite to that of the surfactant used for the dispersant, an inorganic metal salt, and a divalent or higher-valent metal complex are preferably used. In particular, the use of a metal complex is particularly desirable because the amount of the surfactant used can be reduced and the charging characteristics are improved.

As the inorganic metal salt, an aluminum salt and a polymer thereof are particularly suitable. In order to obtain a narrower particle size distribution, the valence of the inorganic metal salt is bivalent than monovalent, trivalent than bivalent, trivalent than trivalent, and tetravalent than trivalent. Inorganic metal salt polymers are more suitable.
In this embodiment, it is desirable to use a polymer of a tetravalent inorganic metal salt containing aluminum in order to obtain a narrow particle size distribution.

(Adhesion process)
In the adhering step, the adhering layer is formed by adhering the binder resin particles to the surface of the agglomerated particles formed through the agglomerated particle forming step (the agglomerated particles provided with the adhering layer on the surface of the agglomerated particles are referred to as “resin Sometimes referred to as "adhesive aggregated particles"). Here, the adhesion layer corresponds to a shell layer formed through a fusion process described later.

  The adhesion layer may be formed by further adding the binder resin particle dispersion to the mixed dispersion in which the aggregated particles are formed in the aggregated particle forming step. In the attaching step, other components such as an aggregating agent may be additionally added as necessary.

  There is no restriction | limiting in particular as the addition mixing method of the binder resin particle dispersion in an adhesion | attachment process, For example, you may carry out gradually continuously and may carry out in steps divided into several times. Thus, by adding and mixing the binder resin particle dispersion, the generation of fine particles is suppressed, and the particle size distribution of the obtained toner particles becomes sharp.

  In the present embodiment, the number of times that this adhesion step is performed may be one or a plurality of times. Multiple layers of shells may be made by changing the resin.

  Conditions for attaching the binder resin particles to the aggregated particles are as follows. That is, the heating temperature in the attaching step may be a temperature range from the glass transition temperature of the binder resin contained in the aggregated particles to the glass transition temperature of the binder resin for the shell layer.

The heating time in the adhesion step depends on the heating temperature and cannot be defined generally, but is usually 5 minutes or more and 2 hours or less.
In addition, in the attaching step, after the binder resin particle dispersion is additionally added to the mixed dispersion in which the aggregated particles are formed, it may be allowed to stand or may be gently stirred by a mixer or the like. . The latter case is advantageous in that uniform resin-adhesive aggregated particles are easily formed.

  In the adhesion step, the amount of the binder resin particle dispersion used depends on the particle size of the binder resin particles contained therein, but the thickness of the finally formed shell layer is about 20 nm to 500 nm. It is desirable to be selected so that

(Fusion process)
In the fusing step, under the stirring conditions according to the agglomerated particle forming step, the pH of the suspension of the resin-adhered agglomerated particles is raised to a range of 3 to 9 to stop the agglomeration, and the binder resin The resin-adhered aggregated particles are fused by heating at a temperature equal to or higher than the glass transition temperature. The heating time may be performed to the extent that fusion is performed, and may be performed for about 0.5 hour to 10 hours.

Cool after fusion to obtain fused particles. Further, in the cooling step, crystallization may be promoted by reducing the cooling rate in the vicinity of the glass transition temperature (range of glass transition temperature ± 10 ° C.) of the resin, so-called slow cooling.
The fused particles obtained by fusing are made into toner particles through a solid-liquid separation process such as filtration and, if necessary, a washing process and a drying process.

  As an external addition method of the external additive to the toner particles, there is a method in which the external additive is added to the toner particles and mixed by a known mixer such as a V-type blender, a Henschel mixer, or a Redige mixer.

(Toner characteristics)
The toner used in the present exemplary embodiment is preferably spherical with a shape factor SF1 in the range of 115 to 140.
As for the shape of the toner, the spherical toner is advantageous in terms of developability and transferability, but may be inferior to the indeterminate shape in terms of cleaning properties. When the toner has a shape in the above range, the transfer efficiency and image density are improved, high-quality image formation is performed, and the cleaning property of the surface of the photoreceptor is enhanced.
The shape factor SF1 is more preferably in the range of 120 to 138.

Here, the shape factor SF1 is obtained by the following equation (2).
SF1 = (ML ² / B) × (π / 4) × 100 (2)
In the above formula (2), ML represents the absolute maximum length of the toner particles, and B represents the projected area of the toner particles.

  SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope (SEM) image using an image analyzer, and is calculated as follows, for example. That is, an optical microscope image of particles scattered on the surface of a slide glass is taken into a Luzex image analyzer through a video camera, the maximum length and projected area of 100 particles are obtained, calculated by the above equation (2), and the average value is calculated. It is obtained by seeking.

  Further, the volume average particle size of the toner used in the exemplary embodiment is desirably 3 μm or more and 9 μm or less, more desirably 3.5 μm or more and 8.5 μm or less, and further desirably 4 μm or more and 8 μm or less. If the volume average particle diameter is 3 μm or more, a decrease in toner fluidity can be suppressed, and the chargeability of each particle can be easily maintained. In addition, the charge distribution does not spread, preventing fogging on the background and preventing toner from spilling from the developer. Further, when the volume average particle diameter of the toner is 3 μm or more, the cleaning property is improved. If the volume average particle size is 9 μm or less, a decrease in resolution can be suppressed, so that a sufficient image quality can be obtained and the recent demand for higher image quality is satisfied.

Note that the volume average particle diameter D _50, Multisizer II - small diameter side volume relative (Beckman Coulter) the measured particle size ranges which are divided based on the particle size distribution measuring apparatus such as a (channel) Then, a cumulative distribution is drawn, and a particle size that is 16% cumulative is defined as volume D _16v , a particle size that is cumulative 50% is _defined as volume D _50v , and a particle size that is cumulative 84% is defined as volume D _84v . Using these, the volume average particle size distribution index (GSDv) is calculated as ( _D84v / _D16v ) ^1/2 .
The GSDv of the toner used in the exemplary embodiment is desirably 1.15 to 1.21 and more desirably 1.15 to 1.19. When the GSDv of the toner is in the above range, the magnetic brush is uniform and the toner is less likely to be unevenly distributed. As a result, the occurrence of image unevenness is suppressed.

  In the developer of this embodiment, the mixing ratio (mass ratio) of the carrier and the toner is preferably in the range of toner: carrier = 1: 100 to 30: 100, and more preferably in the range of 3: 100 to 20: 100. desirable.

<Image Forming Apparatus and Image Forming Method>
Next, the image forming apparatus and the image forming method of the present embodiment using the developer of the present embodiment will be described.
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, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, and the electrostatic image forming unit. Developing means for developing a charge image with the developer of this embodiment to form a toner image, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image to the recording medium . The image forming apparatus according to the present exemplary embodiment may include other means as necessary, for example, a cleaning means for removing the residual transfer component by rubbing the latent image holding member with a cleaning member and cleaning the image forming apparatus. .

  By using 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 latent image holding member, and The present embodiment includes a development step of developing with the 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 is performed.

  Hereinafter, although an example of the image forming apparatus of this embodiment is shown, it is not necessarily limited to this. The main part shown in the figure will be described, and the description of other parts will be omitted.

  In this image forming apparatus, for example, the part including the developing device may have a cartridge structure (process cartridge) that is detachable from the main body of the image forming apparatus. As the process cartridge, a developer holding member is used. The process cartridge of this embodiment that is provided at least and contains the developer of this embodiment is preferably used. The developer holding body conveys the developer to a predetermined position while holding the developer.

  FIG. 1 is a schematic configuration diagram illustrating a four-tandem image forming apparatus as an example of the image forming apparatus according to the present exemplary embodiment. The image forming apparatus shown in FIG. 1 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 simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed 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. It is designed to travel in the direction toward 10K. The support roller 24 is urged away from the drive roller 22 by a spring or the like (not shown), and a predetermined tension is applied to the intermediate transfer belt 20 wound around the support roller 24. 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 includes yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. 4 toners are supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. Note that the second to fourth units 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 10M, 10C, 10K is omitted.

The first unit 10Y has a photoreceptor 1Y that functions as a latent 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 image. An exposure device 3 for developing, a developing device (developing means) 4Y for supplying the charged toner to the electrostatic image and developing the electrostatic image, and a primary transfer roller 5Y (1) for transferring the developed toner image onto the intermediate transfer belt 20 A secondary transfer unit) and a photoconductor cleaning device (cleaning unit) 6Y for removing the toner remaining on the surface of the photoconductor 1Y after the primary transfer.
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 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 converted into a visible image (toner image) by the developing device 4Y.

  In the developing device 4Y, the developer of this embodiment containing yellow toner is accommodated. The developer is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as that charged 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. . 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 predetermined 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 generated. Acting on the toner image, 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 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 and 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 sheet (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 a predetermined secondary transfer bias is applied. Applied 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 sent to a fixing device (fixing means) 28, where the toner image is heated, and the color-superposed toner image is melted and fixed on the recording paper P. 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.

<Process cartridge, toner cartridge>
FIG. 2 is a schematic configuration diagram showing a preferred example of a process cartridge containing the developer according to the present embodiment. In the process cartridge 200, a charging roller 108, a photoconductor 107, a photoconductor cleaning device (cleaning means) 113, an opening 118 for exposure, and an opening 117 for static elimination exposure are mounted on the rail 116 together with the developing device 111. Are combined and integrated with each other. In FIG. 2, reference numeral 300 represents 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 shown in FIG. 2 includes a photoconductor 107, a charging roller 108, a developing device 111, a cleaning device (cleaning means) 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. However, these devices may be selectively combined. In the process cartridge of this embodiment, in addition to the developing device 111, the charging roller 108, the photoconductor 107, the photoconductor cleaning device (cleaning means) 113, the opening 118 for exposure, and the opening for static elimination exposure. It may include at least one selected from the group consisting of the unit 117.

  Next, the toner cartridge of this embodiment will be described. The toner cartridge according to the present exemplary embodiment is a toner cartridge that is attached to and detached from the image forming apparatus and stores at least toner to be supplied to a developing unit provided in the image forming apparatus. It should be noted that at least the toner may be stored in the toner cartridge of this embodiment, and for example, a developer may be stored depending on the mechanism of the image forming apparatus.

  The image forming apparatus shown in FIG. 1 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K are attached and detached. The developing devices 4Y, 4M, 4C, and 4K are the developing devices (colors). 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.

[Example 1]
<Creation of carrier 1>
(Preparation of ferrite particles 1)
1318 parts of Fe ₂ O ₃ , 586 parts of Mn (OH) _{2 and} 96 parts of Mg (OH) ₂ are mixed, pulverized with a dispersant, water and zirconia beads having a media diameter of 1 mm, dried after filtration, and further heated. The temperature was raised to 900 ° C. to obtain an oxide (preliminary firing). Next, 6.59 parts of a dispersant, water, and further polyvinyl alcohol were added and mixed / ground for 10 hours with a wet ball mill. The volume average particle diameter of the oxide after pulverization was 1.8 μm. Further, silica particles having a particle diameter of 30 nm were added in an amount of 0.2% by volume (2.04 parts) of the material, followed by mixing for 2 hours. Next, after granulating and drying with a spray dryer, the temperature was set to 1150 ° C. with an electric furnace and firing was performed for 4.5 hours. Ferrite particles 1 having a particle size of 35 μm were prepared through a crushing step and a classification step. The obtained ferrite particles 1 had Sm of 5 μm, Ry of 0.8 μm, and Ra of 0.4 μm.
Table 1 shows the composition ratio of the raw materials and the firing conditions when preparing the ferrite particles 1. The pulverized particle size shown in Table 1 is a volume average particle size after mixing / pulverization performed after pre-baking. The volume average particle diameter was measured with a laser diffraction particle size distribution measuring apparatus LA-700 (manufactured by Horiba, Ltd.). In addition, Table 2 summarizes the values of Sm, Ry, and Ra of the ferrite particles 1.

(Preparation of coating solution (coating layer forming solution) 1)
・ Cyclohexyl acrylate resin (weight average molecular weight 50,000): 36 parts ・ Carbon black VXC72 (Cabot): 4 parts ・ Toluene: 250 parts ・ Isopropyl alcohol: 50 parts The above components and glass beads (particle size: 1 mm, same amount as toluene) And a coating liquid 1 having a solid content of 11% was prepared by stirring for 30 minutes at a rotational speed of 1200 rpm.

(Preparation of carrier 1)
Place 2000 parts of ferrite particles 1 in a vacuum degassing type 5 L kneader, and further add 560 parts of coating liquid 1. While stirring, reduce the pressure to −200 mmHg at 60 ° C., mix for 15 minutes, and then raise / lower the pressure 94 The coating particles were obtained by stirring and drying at 30 ° C./−720 mHg for 30 minutes. Next, sieving was performed with a 75 μm mesh sieving net to obtain Carrier 1.

<Creation of toner 1>
(Preparation of colorant dispersion 1)
Cyan pigment: Copper phthalocyanine B15: 3 (Daiichi Seika): 50 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts Ion-exchanged water: 200 parts The above is mixed and made by IKA Dispersion was carried out for 5 minutes using an ultra turrax and further for 10 minutes using an ultrasonic bath to obtain a colorant 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 dispersion 1)
Paraffin wax: HNP-9 (Nippon Seiki): 19 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 1 part Ion-exchanged water: 80 parts The above is mixed in a heat-resistant container, 90 The temperature was raised to ° C. and stirring was performed 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 container to 40 ° C. or lower to obtain a release agent dispersion 1. It was 240 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of resin 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 (Rhodia Nikka Co., Ltd.): 3 parts · Dodecanethiol (Wako Pure Chemical Industries, Ltd.): 0.4 parts-water layer 1
・ Ion-exchanged water: 17 parts ・ Anionic surfactant (Dowfax, manufactured by Dow Chemical): 0.4 part-Aqueous layer 2-
・ Ion-exchanged water: 40 parts ・ Anionic surfactant (Dowfax, manufactured by Dow Chemical): 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 emulsion dispersion. The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was sufficiently 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. After completion of the dropping, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours.
The obtained resin particles were 250 nm when the volume average particle diameter D _50v of the resin particles was measured with a laser diffraction particle size distribution measuring apparatus LA-700 (manufactured by Horiba Ltd.). A differential scanning calorimeter (DSC- (50 Shimadzu Corporation) was used to measure the glass transition temperature of the resin at a rate of temperature increase of 10 ° C./min, and it was 52 ° C., using a molecular weight measuring instrument (HLC-8020 manufactured by Tosoh Corporation), and using THF as a solvent and a number average. It was 13,000 when molecular weight (polystyrene conversion) was measured. As a result, a resin dispersion 1 having a volume average particle size of 250 nm, a solid content of 42%, a glass transition temperature of 52 ° C., and a number average molecular weight Mn of 13,000 was obtained.

(Preparation of Toner 1)
-Resin dispersion 1: 150 parts-Colorant dispersion 1: 30 parts-Release agent dispersion 1: 40 parts-Polyaluminum chloride: 0.4 parts The above ingredients are made by IKE in a stainless steel flask. After thorough mixing and dispersion using tarax, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After maintaining at 48 ° C. for 80 minutes, 70 parts of the resin dispersion 1 was gradually added thereto.
Then, after adjusting the pH in the system to 6.0 using a sodium hydroxide aqueous solution having a concentration of 0.5 mol / L, the stainless steel flask was sealed, and the stirring shaft seal was magnetically sealed while stirring was 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, filtered and thoroughly washed with ion-exchanged water, and then solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed using 3 L 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. When the pH of the filtrate was 6.54 and the electric conductivity was 6.5 μS / cm, No. 2 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 mother particles.
The volume average particle diameter D _50v of the toner base particles was measured with a Coulter counter to be 6.2 μm and the volume average particle size distribution index GSDv was 1.19. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135, and it was observed that the particles had a potato shape. The glass transition temperature of the toner mother particles was 52 ° C. Further, the toner base particles are mixed with silica (SiO ₂ ) particles having a primary particle average particle size of 40 nm and subjected to surface hydrophobization treatment with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyltri A metatitanic acid compound particle having an average primary particle diameter of 20 nm, which is a reaction product of methoxysilane, was added so that the coverage with respect to the surface of the toner particles was 40%, and mixed with a Henschel mixer to prepare toner 1. .

<Creation of toner 2>
In the preparation of toner 1, the pH in the system is adjusted to 6.0 using an aqueous solution of sodium hydroxide having a concentration of 0.5 mol / L, the pH is changed to 5.5, heated to 97 ° C. and held for 3 hours. Was prepared in the same manner except that the toner was kept at 94 ° C. for 4 hours.
The volume average particle diameter D _50v of the toner base particles was measured with a Coulter counter and found to be 6.5 μm and the volume average particle size distribution index GSDv was 1.22. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 133, and it was observed that the particles had a potato shape. The glass transition temperature of the toner mother particles was 52 ° C.

<Evaluation>
A Fuji Xerox DCC400 remodeling machine (with toner density sensor disabled, print speed 70 sheets / min) was charged with carrier and toner at the Cyan position so that the toner density would be 2%, 30 ° C, 88% RH In an environment, 50 100% solid patches of 10 cm square were printed on OS coated paper (Fuji Xerox) A4 size. Next, toner was added so that the toner concentration became 12%, and five 10 cm square solid patches were similarly printed. The fifth printed image (solid patch) after the toner concentration of 12% was visually evaluated according to the following criteria. The obtained results are shown in Table 2.

<Evaluation criteria>
A: The image was good with no unevenness.
○: It was good enough to show a slight unevenness visually.
Δ: Some unevenness can be visually confirmed, but there is no unevenness on the entire surface, which is good.
X: Clear unevenness was observed in part of the image.
XX: Unevenness was observed over the entire surface of the image.

[Example 2]
Ferrite particles 2 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 2 were obtained in the same manner as in Example 1. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 2 and toner 1. The obtained results are shown in Table 2.

[Example 3]
Ferrite particles 3 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 3 were obtained in the same manner as in Example 1. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 3 and toner 1. The obtained results are shown in Table 2.

[Example 4]
Ferrite particles 4 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 4 were obtained in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1 by using the obtained carrier 4 and toner 1. The obtained results are shown in Table 2.

[Example 5]
Ferrite particles 5 were prepared according to the composition ratio of the raw materials described in Table 1, firing conditions, and the like, and using this, carriers 5 were obtained in the same manner as in Example 1. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 5 and toner 1. The obtained results are shown in Table 2.

[Example 6]
Ferrite particles 6 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 6 were obtained in the same manner as in Example 1. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 6 and toner 1. The obtained results are shown in Table 2.

[Example 7]
Ferrite particles 7 were prepared according to the composition ratio of the raw materials described in Table 1, firing conditions, and the like, and using this, carriers 7 were obtained in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1 by using the obtained carrier 7 and toner 1. The obtained results are shown in Table 2.

[Comparative Example 1]
Ferrite particles 8 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 8 were obtained in the same manner as in Example 1. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 8 and toner 1. The obtained results are shown in Table 2.

[Comparative Example 2]
Ferrite particles 9 were prepared according to the composition ratio of the raw materials shown in Table 1, firing conditions, and the like, and a carrier 9 was obtained in the same manner as in Example 1 using this. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 9 and toner 1. The obtained results are shown in Table 2.

[Comparative Example 3]
Ferrite particles 10 were prepared according to the composition ratio of raw materials described in Table 1, firing conditions, and the like, and using this, carriers 10 were obtained in the same manner as in Example 1. Evaluation was performed in the same manner as in Example 1 by using the obtained carrier 10 and toner 1. The obtained results are shown in Table 2.

[Comparative Example 4]
Ferrite particles 11 were prepared according to the composition ratio of the raw materials described in Table 1, firing conditions, and the like, and a carrier 11 was obtained in the same manner as in Example 1 using this. Evaluation was conducted in the same manner as in Example 1 using the obtained carrier 11 and toner 1. The obtained results are shown in Table 2.

[Example 8]
The ferrite particles 1 obtained in Example 1 were used as the carrier 12. Evaluation was performed in the same manner as in Example 1 using the carrier 12 and the toner 1. The obtained results are shown in Table 2.

[Example 9]
Evaluation was performed in the same manner as in Example 1 using toner 2 and carrier 1. The obtained results are shown in Table 2.

1Y, 1M, 1C, 1K, 107 photoconductor (latent image holder)
2Y, 2M, 2C, 2K, 108 Charging roller 3Y, 3M, 3C, 3K Laser beam 3 Exposure device 4Y, 4M, 4C, 4K, 111 Developing device (developing means)
5Y, 5M, 5C, 5K Primary transfer rollers 6Y, 6M, 6C, 6K, 113 Photoconductor cleaning device (cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer rollers 28, 115 Fixing device (fixing means)
30 Intermediate transfer member cleaning device 112 Transfer device 116 Mounting rail 117 Opening portion 118 for static elimination exposure Opening portion 200 for exposure Process cartridge P, 300 Recording paper (recording medium)

Claims (7)

Containing at least magnetic particles,
Electrostatic charge development in which the average interval Sm of the irregularities on the surface of the magnetic particles and the maximum height Ry of the surface of the magnetic particles are 3.6 μm ≦ Sm ≦ 8.0 μm and 0.5 μm ≦ Ry ≦ 1.0 μm For carrier.   2. The electrostatic charge developing carrier according to claim 1, wherein the arithmetic average roughness Ra of the surface of the magnetic particles is 0.1 μm ≦ Ra ≦ 0.5 μm.   The electrostatic charge developing carrier according to claim 1, further comprising a coating layer covering a surface of the magnetic particle.   The electrostatic image developing developer comprising: the electrostatic charge developing carrier according to any one of claims 1 to 3; and a toner having a volume average particle size distribution index GSDv of 1.15 to 1.21. Agent.   A process cartridge comprising at least a developer holder and containing the developer for developing an electrostatic image according to claim 4.   5. The latent image holding member, a charging unit that charges the surface of the latent image holding member, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge image according to claim 4. An image comprising: a developing unit that develops a toner image by developing with a developer for developing an electrostatic image; a transfer unit that transfers the toner image to a recording medium; and a fixing unit that fixes the toner image on the recording medium. Forming equipment.   5. The developer for developing an electrostatic charge image according to claim 4, wherein 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 latent image holding member, and the electrostatic charge image are developed. An image forming method comprising: a developing step for forming a toner image by developing the toner image; a transfer step for transferring the toner image onto a recording medium; and a fixing step for fixing the toner image on the recording medium.