JP2013148736A - Carrier for electrostatic charge development, developer for electrostatic charge development, image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge development preventing aggregation of toner for electrostatic charge development.SOLUTION: A carrier for electrostatic charge development includes magnetic particles with a circularity of 0.950 or more and 0.990 or less and a volume particle size distribution satisfying a relationship of following formula (1):1.5≤(C-A)/(A-B)≤3.5, and a coating resin layer coating the magnetic particles. In the formula (1), A represents a peak particle size (μm) in the volume particle size distribution, B represents a minimum particle size (μm) of particle sizes at frequency of 2% in the volume particle size distribution, and C represents a maximum particle size (μm) of particle sizes at frequency of 2% in the volume particle size distribution.

Description

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

  In electrophotography, an electrostatic latent image formed on the surface of an electrostatic latent image holding member (photoreceptor) is developed with toner containing a colorant, and the obtained toner image is transferred to the surface of a recording medium. An image can be obtained by fixing with a heat roll or the like. In addition, the latent image holding member is cleaned with residual toner to form an electrostatic latent image again, and the cleaning step is omitted when there is almost no residual toner as in the case of using spherical toner. In some cases. As described above, dry developers used for electrophotography and the like are divided into a one-component developer using a toner in which a binder is mixed with a colorant and the like, and a two-component developer in which the toner is mixed with a carrier. Broadly divided.

  As a carrier used for a two-component developer, for example, in Patent Document 1, “in a carrier for developing an electrostatic latent image having a resin coating layer on the surface of a carrier core, the shape factor SF-1 of the core is 100 to 110. And a carrier for developing an electrostatic latent image characterized in that the variation coefficient of SF-1 is 15% or less.

Further, in Patent Document 2, “a resin-coated carrier for a two-component developer having a carrier core material and carrier particles having a coating layer for coating the surface of the carrier core material, % Particle size C (D ₅₀ ) of 25 to 70 μm, 0.1 to 20% by number of carrier particles smaller than 22 μm, 2 to 35% by number of carrier particles of 62 μm or more, The BET specific surface area SW1 of the carrier core material from which the coating layer has been removed and the BET specific surface area SW2 of the resin-coated carrier satisfy the formula (I): 80 ≦ SW1-SW2 ≦ 650 (cm ² / g), and the resin The coat carrier satisfies the shape factor SF-1 of formula (II): 110 ≦ SF-1 ≦ 160 and the shape factor SF-2 of formula (III) below: 105 ≦ SF-2 ≦ 150. A resin-coated carrier for a two-component developer characterized by the above has been proposed.

  In Patent Document 3, “at least a magnetic carrier having a resin coating layer formed on the surface of a magnetic carrier core, the resin coating layer containing at least a resin composition and carbon black particles, and the resin coating layer is made of toluene. In the volume-based particle size distribution measurement of the particles when dissolved in the above, the maximum peak particle size Pv is 0.10 μm or more and 1.00 μm or less, and the maximum peak half-value width Hv is 0.05 μm or more and 0.40 μm or less. A magnetic carrier characterized in that the frequency ratio Fv occupied by the maximum peak with respect to the total peak frequency satisfies 65% to 95% ”has been proposed.

  Further, in Patent Document 4, “in the method for producing a carrier for developing an electrostatic latent image having a magnetic core material particle and a coating layer on the particle surface, the carrier has a weight average particle diameter Dw of 22 to 32 μm, and The ratio of the number average particle diameter Dp to the weight average particle diameter Dw (Dw / Dp) is 1.0 <Dw / Dp <1.2, and the content of particles having a particle diameter of less than 20 μm is 0 to 7 wt. %, A particle size distribution in which the content of particles smaller than 36 μm is 90 to 100% by weight, and the core material particles are obtained by mixing a plurality of particle powders having different particle size distributions A method for producing a carrier for developing an electrostatic latent image has been proposed.

JP 2009-103782 A JP 2000-172019 A JP 2011-33861 A JP 2006-64713 A

  An object of the present invention is to provide an electrostatic charge developing carrier that suppresses aggregation of the electrostatic charge developing toner.

The above problem is solved by the following means.
That is, the invention according to claim 1
Magnetic particles having a circularity of 0.950 or more and 0.990 or less and a volume particle size distribution satisfying the relationship of the following formula (1):
A coating resin layer that coats the magnetic particles;
An electrostatic charge developing carrier having:
Formula (1): 1.5 ≦ (C−A) / (A−B) ≦ 3.5
(In Formula (1), A shows the peak particle size (μm) in the volume particle size distribution. B shows the minimum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution. (The maximum particle size (μm) is shown among the particle sizes having a frequency of 2% in the volume particle size distribution.)

The invention according to claim 2
The carrier for electrostatic charge development according to claim 1, wherein a peak particle size in a volume particle size distribution of the magnetic particles is 20 μm or more and 30 μm or less.

The invention according to claim 3
3. The electrostatic charge developing carrier according to claim 1, wherein the average irregularity interval Sm on the surface of the magnetic particle is 1.5 μm or more and 3.5 μm or less.

The invention according to claim 4
4. The electrostatic charge developing carrier according to claim 1, wherein the surface roughness Ra of the magnetic particles is 0.1 μm or more and 0.5 μm or less. 5.

The invention according to claim 5
An electrostatic charge developing developer comprising a toner and the electrostatic charge developing carrier according to claim 1.

The invention according to claim 6
The developer for electrostatic charge development according to claim 5 is contained, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the developer for electrostatic charge development to form a toner image. With developing means,
A process cartridge that is detachable from the image forming apparatus.

The invention according to claim 7 provides:
An electrostatic latent image carrier;
Charging means for charging the surface of the electrostatic latent image holding member;
Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrostatic latent image holding member;
An electrostatic charge developing developer according to claim 5 is accommodated, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the electrostatic charge developing developer to form a toner image. Developing means to form;
Transfer means for transferring the toner image to a recording medium;
Fixing means for fixing a toner image on the recording medium;
An image forming apparatus comprising:

The invention according to claim 8 provides:
A charging step for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming step of forming an electrostatic charge image on the surface of the charged electrostatic latent image holding member;
A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member to form a toner image by the electrostatic charge developing developer according to claim 5;
A transfer step of transferring the toner image to a recording medium;
A fixing step of fixing a toner image on the recording medium;
An image forming method comprising:

According to the first aspect of the present invention, the aggregation of the electrostatic charge developing toner is suppressed as compared with the case of having magnetic particles that do not satisfy the circularity range and whose volume particle size distribution does not satisfy the relationship of the formula (1). An electrostatic charge developing carrier can be provided.
According to the second aspect of the present invention, even if the peak particle size distribution in the volume particle size distribution of the magnetic particles is such that the electrostatic charge developing toner is likely to agglomerate, it does not satisfy the circularity range and the volume. Compared to the case where the particle size distribution has magnetic particles that do not satisfy the relationship of formula (1), it is possible to provide an electrostatic charge developing carrier that suppresses aggregation of the electrostatic charge developing toner.
According to the inventions according to claims 3 and 4, for electrostatic charge development, which suppresses aggregation of toner for electrostatic charge development, compared to the case where the average irregularity interval Sm or arithmetic surface roughness Ra of the surface of the magnetic particles is outside the above range. Can provide a career.

  According to the inventions according to claims 5, 6, 7, and 8, an electrostatic charge developing carrier having magnetic particles that do not satisfy the circularity range and whose volume particle size distribution does not satisfy the relationship of the formula (1) is applied. As compared with the above case, it is possible to provide an electrostatic charge developing developer, a process cartridge, an image forming apparatus, and an image forming method capable of obtaining an image in which image defects due to aggregation of electrostatic charge developing toner are suppressed.

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 which concerns on this embodiment. It is a schematic diagram for demonstrating the volume particle size distribution of the electrostatic charge developing carrier which concerns on this embodiment.

[Carrier for electrostatic charge development]
The electrostatic charge developing carrier (hereinafter, simply referred to as “carrier”) according to the present embodiment includes magnetic particles and a coating resin layer that covers the magnetic particles.
The magnetic particles have a circularity of 0.950 or more and 0.990 or less and satisfy the relationship of the following formula (1).
Formula (1): 1.5 ≦ (C−A) / (A−B) ≦ 3.5
(In Formula (1), A shows the peak particle size (μm) in the volume particle size distribution. B shows the minimum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution. (The maximum particle size (μm) is shown among the particle sizes having a frequency of 2% in the volume particle size distribution.)

  Here, if the circularity of the magnetic particles is 0.950 or more and 0.990 or less, the fluidity of the carrier is increased due to the spherical shape, while the electrostatic charge developing toner using the carrier (hereinafter referred to as “toner”). In some cases, the toner agglomerates even though it is considered that the mechanical load on the toner is reduced. This is because when the developer for electrostatic charge development (hereinafter referred to as “developer”) flows, the toner enters the gap between the carrier particles, and as a result, the toner is compressed between the carrier particles. This is because it is considered.

Accordingly, in the carrier according to the present embodiment, the circularity of the magnetic particles is set to 0.950 or more and 0.990 or less, and the volume particle size distribution of the magnetic particles is adjusted so as to satisfy the formula (1). When the agent flows, it is suppressed that the toner is compressed by the carrier, and as a result, aggregation of the toner is suppressed.
The reason for this is not clear, but is considered as follows.

First, the volume particle size distribution of the magnetic particles satisfies the formula (1). In the volume particle size distribution, the particle size distribution on the smaller side from the minimum particle size B to the peak particle size A is the peak particle. This means that the particle size distribution on the larger side from the diameter A to the maximum particle diameter C is small in an appropriate range such as the above range (see FIG. 3). This is considered to mean that relatively small carrier particles are appropriately interposed in the gaps between the large-sized carrier particles to reduce the gaps.
That is, when the volume particle size distribution of the magnetic particles satisfies the formula (1), the gap between the carrier particles is narrowed, and when the developer flows, it becomes difficult for the toner to enter the gap between the carrier particles. It is considered that the toner is suppressed from being compressed between the particles.

From the above, it is considered that toner aggregation is suppressed in the carrier according to the present embodiment.
In particular, the mechanical load on the toner due to the carrier increases under high temperature, high humidity, and high speed printing conditions. Even under such conditions, the carrier according to the present embodiment is considered to suppress toner aggregation. .
Then, when the carrier according to the present embodiment is applied to an electrostatic charge developing carrier, an electrostatic charge developing developer, an electrostatic charge developing developer cartridge, a process cartridge, an image forming apparatus, and an image forming method, the toner is aggregated. An image with suppressed image defects (for example, color points) and other image defects (for example, white spots, fog, etc.) can be obtained.

  Hereinafter, details of the carrier according to the present embodiment will be described.

Examples of magnetic particles include magnetic metal particles (for example, particles of iron, steel, nickel, cobalt, etc.), magnetic oxide particles (for example, particles of ferrite, magnetite, etc.), and a magnetic particle dispersed resin in which these particles are dispersed in a resin. Particles and the like.
In particular, the magnetic particles are preferably ferrite particles represented by the following formula, for example.

Formula: (MO) _X (Fe ₂ O ₃ ) _Y
In the formula, Y represents 2.1 or more and 2.4 or less, and X represents 3-Y. M represents a metal element, and preferably contains at least Mn as the metal element.
M is mainly composed of Mn, but is composed of Li, Ca, Sr, Sn, Cu, Zn, Ba, Mg, and Ti (preferably from the viewpoint of environment, from Li, Ca, Sr, Mg, and Ti). You may combine at least 1 type selected from the group which consists of.

The circularity of the magnetic particles is 0.950 or more and 0.990 or less, preferably 0.96 or more and 0.985 or less, and more preferably 0.975 or more and 0.985 or less.
When the circularity of the magnetic particles is less than 0.95, the fluidity of the developer is deteriorated, the mechanical load on the toner by the carrier is increased, and toner aggregates are liable to occur.
If the circularity of the magnetic particles exceeds 0.990, the fluidity of the developer is excessively increased, so that the toner is less likely to be triboelectrically charged by the carrier.

Here, the circularity of the magnetic particles means an average circularity measured by the following method.
First, the coating resin layer is removed from the carrier (for example, removed by dissolving in a solvent) to obtain magnetic particles.
200 mg of the obtained magnetic particles are added to 30 ml of an ethylene glycol aqueous solution and stirred, and the residue from which the supernatant aqueous solution has been removed is obtained as a measurement sample.
And it measures using the obtained measurement sample. For the measurement, FPIA-3000 (manufactured by Sysmex Corporation) is used, and image analysis is performed on each of the photographed magnetic particles of at least 5000 or more, and the average circularity is obtained by statistical processing. Here, each circularity is calculated | required based on a following formula.
Formula: Circularity = circle equivalent diameter perimeter / perimeter = [2 × (A × π) ^1/2 ] / PM
In the formula, A represents the projected area of the magnetic particles, and PM represents the perimeter of the magnetic particles. )
The measurement is performed in the HPF mode (high resolution mode) and the dilution factor of 10 times. In the data analysis, the number particle size analysis range was 3 μm or more and 80 μm or less and the circularity analysis range was 0.850 or more and 1.000 or less for the purpose of removing measurement noise.

The volume particle size distribution of the magnetic particles satisfies the relationship of the following formula (1) (preferably the relationship of formula (1-2), more preferably the relationship of formula (1-3)).
Formula (1): 1.5 ≦ (C−A) / (A−B) ≦ 3.5
Formula (1-2): 2.0 ≦ (C−A) / (A−B) ≦ 3
Formula (1-3): 2.4 ≦ (C−A) / (A−B) ≦ 2.6

  In the formulas (1) to (1-3), A represents a peak particle size (μm) in the volume particle size distribution. B represents the minimum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution. C represents the maximum particle size (μm) among particle sizes having a frequency of 2% in the volume particle size distribution.

In the volume particle size distribution of the magnetic particles, when “(C−A) / (A−B)” is less than 1.5, the gap between the carrier particles becomes large, and the toner easily enters the gap. The toner tends to aggregate.
In the volume particle size distribution of the magnetic particles, if “(C−A) / (A−B)” exceeds 3.5, the volume particle size distribution is too wide on the coarse particle side, so that the variation in charge of the toner increases and fogging occurs. Is likely to occur.

The peak particle size A in the volume particle size distribution of the magnetic particles is, for example, preferably from 20 μm to 30 μm, desirably from 22 μm to 28 μm, and more desirably from 24 μm to 25 μm.
When the peak particle size of the magnetic particles is within the above range, toner aggregation is likely to occur, but this is likely to be reduced.
In particular, when the peak particle size of the magnetic particles is 20 μm or more, carrier scattering to the electrostatic latent image holding member (photosensitive member) is suppressed, and the generation of white spots is easily suppressed.
When the peak particle size of the magnetic particles is 30 μm or less, the mechanical load on the toner by the carrier is reduced, and toner aggregation is easily suppressed.

In addition, the minimum particle size among the particle sizes having a frequency of 2% in the volume particle size distribution of the magnetic particles is, for example, preferably 14 μm or more and 26 μm, desirably 18 μm or more and 25 μm or less, and more desirably 24 μm or more and 25 μm or less.
The maximum particle size among the particle sizes having a frequency of 2% in the volume particle size distribution of the magnetic particles is, for example, preferably 30 μm to 55 μm, desirably 32 μm to 40 μm, and more desirably 34 μm to 38 μm.

Here, the volume particle size distribution of the magnetic particles is obtained as follows.
First, the coating resin layer is removed from the carrier (for example, removed by dissolving in a solvent) to obtain magnetic particles.
About the obtained magnetic particle, it measures using the laser diffraction type particle size distribution measuring apparatus "LA-700 (made by Horiba, Ltd.)", and obtains the volume particle size distribution of a magnetic particle.
Specifically, the cumulative distribution is drawn from the small diameter side with respect to the particle size range (channel) obtained by dividing the value obtained by the laser diffraction particle size distribution measuring device, and the volume particle size distribution of the magnetic particles is obtained.
In the volume particle size distribution of the magnetic particles, the particle size showing the highest frequency (%) is the peak particle size, and the particle size of frequency 2 (%) is the smaller particle size is the minimum particle size, the larger one Is defined as the maximum particle size.

The average irregularity interval Sm on the surface of the magnetic particles is, for example, 1.4 μm or more and 3.5 μm or less (preferably 1.5 μm or more and 3 μm or less, more preferably 2.5 μm or more and 2.6 μm or less). The arithmetic surface roughness Ra is, for example, 0.08 μm or more and 0.7 μm or less, preferably 0.1 μm or more and 0.6 μm or less, and more preferably 0.3 μm or more and 0.6 μm or less.
In particular, it is preferable that the average irregularity interval Sm on the surface of the magnetic particles is 1.5 μm or more and 3.5 μm or less, and the arithmetic surface roughness Ra of the surface of the magnetic particles is 0.1 μm or more and 0.5 μm or less.

The magnetic particles having the average roughness Sm and / or the arithmetic surface roughness Ra of the surface of the magnetic particles with the circularity of the magnetic particles within the above range have no notches and the like, and have unevenness on the entire surface. This means that the developer is fluid and the mechanical load on the toner by the carrier is reduced. As a result, toner agglomerates are less likely to occur.
In addition, when the unevenness average interval Sm and / or the arithmetic surface roughness Ra on the surface of the magnetic particles are within the above ranges, the density of the magnetic brush is stabilized and the image quality is improved. Note that the magnetic brush means that a plurality of carriers to which toner adheres are linearly connected to the surface of the developer holding body to form spikes by the magnetic force of the magnet contained in the developer holding body (developing roll). Means the state

In particular, when the unevenness average interval Sm on the surface of the magnetic particles is 1.4 μm or more, the grain boundary on the surface of the carrier particles is not too small, the variation in magnetization between the carrier particles is reduced, and the magnetic brush is easily stabilized.
When the unevenness average interval Sm on the surface of the magnetic particle is 3.5 or less, the grain boundary on the surface of the carrier particle is not too large, and the magnetic brush is prevented from becoming rough, and the magnetic brush is easily stabilized.
On the other hand, when the arithmetic surface roughness Ra of the surface of the magnetic particles is set to 0.08 or more, the convex portions on the surface of the carrier particles are not too small, and the magnetic brush slips (that is, slips between successive carrier particles constituting the magnetic brush). ) Is suppressed, and the magnetic brush is easily stabilized.
When the arithmetic surface roughness Ra of the surface of the magnetic particles is less than 0.7, the convex portions on the surface of the carrier particles are not too large, and the magnetic brush is prevented from becoming rough, and the magnetic brush is easily stabilized.

Here, the unevenness average interval Sm and the arithmetic surface roughness Ra of the surface of the magnetic particles are obtained as follows.
First, the coating resin layer is removed from the carrier (for example, removed by dissolving in a solvent) to obtain magnetic particles.
The obtained 50 magnetic particles are obtained by observing the surface at a magnification of 3000 times using an ultra-deep color 3D shape measurement microscope (VK-9500, manufactured by Keyence Corporation).
The average interval Sm of the irregularities is obtained from the observed three-dimensional shape of the surface of the magnetic particle, 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.
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.
The Sm value and Ra value are measured according to JIS B 0601 (1994 version).

Next, a method for producing magnetic particles satisfying the above characteristics will be described.
For example, magnetic particles satisfying the above characteristics are produced as follows.
First, the raw materials are mixed and heated to form an oxide.
Next, the oxide is pulverized and mixed with zirconia beads together with water, a dispersant, and polyvinyl alcohol.
Next, the pulverized oxide is dried into particles by spray drying, and is fired and sintered in a firing furnace. Control the temperature and oxygen concentration to produce magnetic particles.

Here, in the production process, when the oxide is pulverized and mixed, the volume particle size distribution of the pulverized oxide particles is adjusted to satisfy D90v / D50v ≦ 4.5. Thereby, the unevenness of the sintering speed during firing is easily reduced. When the unevenness of the sintering speed between the oxide particles is reduced, the variation in the degree of deformation between the oxide particles is reduced, and the small diameter occurrence rate is likely to be lowered.
Here, the volume particle size distribution of the oxide particles is based on the particle size range (channel) obtained by dividing the value obtained by the laser diffraction particle size distribution analyzer “LA-700 (manufactured by Horiba, Ltd.)”. The cumulative distribution is drawn from the small diameter side with respect to the volume.
In the volume particle size distribution of the oxide particles, the particle size at which accumulation from the small diameter side is 50% is defined as D50V, and the particle size at which accumulation from the small diameter side is 90% is defined as D90v.

Also, in this production process, the magnetic particles produced by firing and sintering are sieved with a sieving mesh, and after aligning the particle size, the particles are attached to a magnetic drum and rotated to rotate the coarse particles, irregular particles, and small particles. It is better to sort. Atypical particles and small-diameter particles have low magnetization and are easy to sort with a drum. In addition, it is good to use air blow together.
By these operations. Magnetic particles having the desired volume particle size distribution can be easily obtained, and at the same time, irregularly shaped particles are removed, and magnetic particles having the desired circularity are easily obtained.

For example, when SiO ₂ and CaCO ₃ are added by pulverization and mixing of oxides during the production of magnetic particles, the surface irregularities are adjusted, so that the target circularity, irregular average spacing Sm and arithmetic surface roughness are adjusted. It becomes easy to obtain magnetic particles of thickness Ra.

(Coating resin layer)
Examples of the coating resin constituting the coating resin layer include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic. Examples include an acid copolymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, and an epoxy resin.

The coating resin layer may contain other additives such as a conductive material, for example.
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 preferable because of excellent production stability.

In order to form the coating resin layer on the surface of the magnetic particles, for example, a method of coating with a coating resin and a solution for forming a coating resin layer in which various additives are dissolved in an appropriate solvent as necessary may be mentioned. The solvent is not particularly limited, and may be selected in consideration of the coating resin to be used, coating suitability, and the like.
Specific methods include an immersion method in which the core material is immersed in the coating resin layer forming solution, a spray method in which the coating layer forming solution is sprayed on the surface of the core material, and the magnetic particles are coated in a state of being suspended by fluid air. Examples thereof include a fluidized bed method in which a resin layer forming solution is sprayed, a kneader coater method in which magnetic particles of a carrier and a coating resin layer forming solution are mixed in a kneader coater, and the solvent is removed.

  Here, the coating amount of the coating resin layer on the magnetic particles is, for example, 0.5% by mass or more (preferably 0.7% by mass or more and 6% by mass or less, more preferably 1.0% by mass with respect to the mass of the entire carrier. % To 5.0% by mass).

Here, the coating amount is obtained as follows.
In the case of a solvent-soluble coating resin, a precise amount of carrier is dissolved in a soluble solvent (for example, toluene), the magnetic powder is held by a magnet, and the solution in which the coating resin is dissolved is washed away. By repeating this several times, the magnetic powder from which the clothing resin has been removed remains. The coating amount is calculated by drying, measuring the mass of the magnetic powder, and dividing the difference by the carrier amount.
Specifically, 20.0 g of the carrier is measured, put into a beaker, 100 g of toluene is added, and the mixture is stirred with a stirring blade for 10 minutes. A magnet is applied to the bottom of the beaker, and toluene is allowed to flow so that the core material (magnetic powder) does not flow out. This is repeated 4 times, and the beaker after washing is dried. After drying, the amount of magnetic powder is measured, and the coating amount is calculated by the formula [(carrier amount−magnetic powder amount after washing) / carrier amount].
On the other hand, in the case of a solvent-insoluble coating resin, Rigaku's Thermo plus EVOII differential type differential thermobalance TG8120 is heated in a nitrogen atmosphere in the range of room temperature (25 ° C.) to 1000 ° C., and its mass is reduced. From this, the coating amount is calculated.

[Developer for electrostatic charge development]
The developer according to the present embodiment is a so-called two-component developer including the toner and the carrier according to the present embodiment.

Next, the toner will be described.
The toner includes, for example, a toner particle containing a binder resin and other additives such as a colorant and a release agent as necessary, and an external additive as necessary.

The toner particles will be described.
The binder resin is not particularly limited, but styrenes (eg, styrene, chlorostyrene, etc.), monoolefins (eg, ethylene, propylene, butylene, isoprene, etc.), vinyl esters (eg, vinyl acetate, vinyl propionate, Vinyl benzoate, vinyl butyrate, etc.), α-methylene aliphatic monocarboxylic acid esters (eg methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, methacrylic acid) Ethyl acetate, butyl methacrylate, dodecyl methacrylate, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether), vinyl ketones (eg, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopro) Homopolymers and copolymers of Niruketon etc.), etc., and polyester resins by copolymerization of dicarboxylic acids and diols.

Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include a polymer, a polyethylene resin, a polypropylene resin, and a polyester resin.
Typical binder resins include polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.

  Examples of the colorant include magnetic powder (eg, magnetite, ferrite, etc.), carbon black, aniline blue, caryl 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 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

Examples of other additives include mold release agents, magnetic substances, charge control agents, inorganic powders, and the like.
Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester types such as fatty acid esters and montanic acid esters. Wax; and the like, but is not limited thereto.

The characteristics of the toner particles will be described.
Average shape factor of toner particles (shape factor = (ML ² / A) × (π / 4) × 100) average number of shape factors represented by ML, where ML represents the maximum length of particles, and A represents the projection of particles The area is preferably 100 or more and 150 or less, more preferably 105 or more and 145 or less, and even more preferably 110 or more and 140 or less.

  The volume average particle size of the toner is preferably, for example, from 3.0 μm to 9 μm, more preferably from 3.5 μm to 8.5 μm, and even more preferably from 4 μm to 8 μm.

Here, the method for measuring the volume average particle diameter of the toner particles is as follows.
First, 0.5 mg to 50 mg of a measurement sample was added to 2 ml of a 5 mass% aqueous solution of a surfactant (desirably sodium alkylbenzenesulfonate) as a dispersant, and this was added to 100 ml to 150 ml of an electrolytic solution. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and a particle size is measured with a Coulter Multisizer II type (manufactured by Beckman-Coulter) using an aperture having an aperture diameter of 100 μm Is a particle size distribution of particles in the range of 2.0 μm or more and 60 μm or less. The number of particles to be measured is 50,000.
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 that becomes 50% cumulative is defined as the volume average particle size D50v.

The external additive will be described.
Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, and CaO. , K ₂ O, Na ₂ O, ZrO ₂ , CaO.SiO ₂ , K ₂ O. (TiO ₂ ) _n , Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO _{4 and the} like. .

  The surface of the external additive may be hydrophobized in advance. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents and the like. These may be used individually by 1 type and may use 2 or more types together.

Next, a toner manufacturing method will be described.
First, the toner particles are not particularly limited by the production method. For example, the toner particles are kneaded and pulverized by adding, for example, a binder resin, a colorant and a release agent, and a charge control agent as necessary. Method: Method of changing the shape of particles obtained by kneading and pulverization method by mechanical impact force or thermal energy; Emulsion polymerization of polymerizable monomer of binder resin, and formed dispersion and colorant And a release agent and, if necessary, a dispersion of a charge control agent or the like, and agglomeration, heat fusion to obtain toner particles; an emulsion polymerization aggregation method; a polymerizable monomer for obtaining a binder resin; A suspension polymerization method in which a solution of a colorant and a release agent, if necessary, a charge control agent is suspended in an aqueous solvent for polymerization; a binder resin, a colorant and a release agent, and optionally charged A solution manufactured by a suspension method, etc., in which a solution of a control agent is suspended in an aqueous solvent and granulated. Over particles are used.

  Further, a known method such as a production method in which the toner particles obtained by the above method are used as a core, and agglomerated particles are further adhered and heated and fused to give a core-shell structure is used.

As a method for producing the toner particles, a suspension polymerization method, an emulsion polymerization aggregation method, and a dissolution suspension method in which an aqueous solvent is used are desirable from the viewpoint of shape control and particle size distribution control, and an emulsion polymerization aggregation method is particularly desirable.
In particular, according to these production methods, since the surface irregularity of the toner particles is small and smooth, the pressure on the toner by the carrier is relieved, and as a result, the occurrence of toner aggregation is easily suppressed.

  The toner is produced by mixing the toner particles and the external additive with a Henschel mixer or a V blender. Further, when the toner particles are produced by a wet method, they may be externally added by a wet method.

  The toner and the carrier in the developer according to the exemplary embodiment are mixed at a ratio of, for example, 1: 100 to 30: 100 (toner: carrier, mass ratio).

[Image Forming Apparatus and Image Forming Method]
Next, an image forming apparatus and an image forming method according to this embodiment using the developer according to this embodiment will be described.

  The image forming apparatus according to the present embodiment includes an electrostatic latent image holding member, a charging unit that charges the surface of the electrostatic latent image holding member, and an electrostatic latent image that forms an electrostatic latent image on the surface of the electrostatic latent image holding member. An electrostatic latent image forming unit and a developing unit that stores the developer according to the present embodiment and forms a toner image by developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the developer. And a cleaning unit including a transfer unit that transfers the toner image to the recording medium and a fixing unit that fixes the toner image on the recording medium.

  According to the image forming apparatus according to the present embodiment, the charging step of charging the surface of the electrostatic latent image holding member and the electrostatic latent image forming step of forming an electrostatic charge image on the surface of the charged electrostatic latent image holding member. A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the developer according to the present embodiment to form a toner image, and a transfer step of transferring the toner image to a recording medium And a fixing process for fixing the toner image on the recording medium.

  Image formation in the image forming apparatus according to the present embodiment is performed, for example, as follows when an electrophotographic photosensitive member is used as the electrostatic latent image holding member. First, the surface of the electrophotographic photosensitive member is charged by a corotron charger, a contact charger or the like and then exposed to form an electrostatic charge image. Next, the toner is attached to the electrostatic latent image in contact with or in proximity to a developing roll having a developer layer formed on the surface, thereby forming a toner image on the electrophotographic photosensitive member. The formed toner image is transferred onto the surface of a recording medium such as paper using a corotron charger or the like. Further, the toner image transferred to the surface of the recording medium is fixed by a fixing device, and an image is formed on the recording medium.

In the image forming apparatus according to the present embodiment, for example, the part including the developing unit may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus.
As the process cartridge, for example, the electrostatic charge developing developer according to this embodiment is accommodated, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed by the electrostatic charge developing developer. A process cartridge that includes a developing unit that forms a toner image and is detachable from the image forming apparatus is preferably used.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

  FIG. 1 is a schematic configuration diagram showing a four-tandem color image forming apparatus. 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 sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed at a predetermined distance from each other. 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 toner including the four color toners can be 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 cleaning, and a photoreceptor cleaning device (cleaning unit) 6Y that includes a cleaning blade 6Y-1 that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer are sequentially arranged. ing.
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 according to the present embodiment including 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. . 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, a primary transfer bias is applied to the primary transfer roller 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roller 5Y acts on the toner image. Then, the toner image on the photoreceptor 1Y 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 blade 6Y-1 of 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, the recording paper (transfer object) P is fed at a predetermined timing to the gap where the secondary transfer roller 26 and the intermediate transfer belt 20 are pressed against each other via the supply mechanism, and the secondary transfer bias is supported. Applied to the 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 transfer target to which the toner image is transferred include plain paper and OHP sheet used for electrophotographic copying machines, printers, and the like.
In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer target is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with a resin or the like, for printing Art paper or the like is preferably used.

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]
FIG. 2 is a schematic configuration diagram showing an embodiment of a preferred example of a process cartridge containing an electrostatic charge image developer according to this embodiment. The process cartridge 200 includes, together with the photoconductor 107, a charging roller 108, a developing device 111, a photoconductor cleaning device 113 having a cleaning blade 113-1, an opening 118 for exposure, and an opening 117 for static elimination exposure. Attachment, combination using rails 116, and integration. In FIG. 2, reference numeral 300 denotes a transfer target.
The process cartridge 200 is detachable from an image forming apparatus including a transfer device 112, a fixing device 115, and other components not shown.

  The process cartridge 200 shown in FIG. 2 includes 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. Can be combined. In the process cartridge according to the present embodiment, in addition to the photosensitive member 107, the charging device 108, the developing device 111, the cleaning device (cleaning means) 113, the opening 118 for exposure, and the opening for static elimination exposure. 117, at least one selected from the group consisting of 117.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In the following Examples, “part” and “%” mean “part by mass” and “% by mass”, respectively, unless otherwise specified.

[Preparation of magnetic particles]
(Magnetic particles (1))
Fe ₂ O ₃ : 1320 parts by mass, Mn (OH) ₂ : 580 parts by mass, and Mg (OH) ₂ : 96 parts by mass were mixed, the temperature was raised to 900 ° C., and calcined to obtain an oxide. .
Next, 800 parts by mass of water and 25 parts by mass of polyvinyl alcohol (PVA) were further added to the obtained oxide and mixed / pulverized with a wet ball mill for 10 hours.
Further, 1.5 parts by mass of SiO ₂ was further added, followed by pulverization and mixing. This pulverization and mixing was performed until “D90v / D50v” of the pulverized oxide became 4.5 or less.
Next, the mixture was granulated and dried with a spray dryer so that the center particle diameter of the oxide was 26 μm, and then the temperature was set to 1150 ° C. in an electric furnace and baked for 5 hours to obtain magnetic particles.
After sieving the obtained magnetic particles with a 45 μm sieving mesh, they were attached to the magnetic drum so as to form a thin layer, and rotated while performing air blowing to obtain the desired volume particle size distribution (see Table 2). By the way it ended.
In this way, magnetic particles (1) were prepared.

(Magnetic particles (2) to (18))
According to Table 1, the magnetic particles (2) to (18) were obtained in the same manner as the magnetic particles (1) except that the production conditions were changed.
However, the air blow process using the magnetic drum performed on the magnetic particles after sieving with the obtained sieving screen is the volume particle size distribution targeted by each of the magnetic particles (2) to (18) (see Table 2). ) So that it ends.
Moreover, only the magnetic particle (10) used 53 micrometers of sieving nets.
CaCO ₃ was added instead of SiO ₂ .

[Example 1]
(Resin coating layer forming solution: coating solution (1))
Cyclohexyl acrylate resin (weight average molecular weight 50,000): 36 parts by mass Carbon black “VXC72 (manufactured by Cabot)”: 4 parts by mass Toluene: 250 parts by mass Isopropyl alcohol: 50 parts by mass The above components and glass beads (particles) (Diameter: 1 mm, the same amount as toluene) was put into a sand mill manufactured by Kansai Paint Co., Ltd. and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a coating liquid (1) having a solid content of 11%.

(Career)
After putting 2000 parts by mass of magnetic particles (1) into a vacuum degassing type 5 L kneader, and further adding 560 parts by mass of coating liquid (1), the mixture was stirred at 60 ° C. under reduced pressure to −200 mmHg for 15 minutes, The temperature was increased / decreased and the mixture was stirred and dried at 94 ° C./−720 mHg for 30 minutes to obtain magnetic particles coated with the coating resin layer.
Next, the obtained particles were sieved with a 75 μm mesh sieve to obtain a carrier.
The obtained carrier was used as the carrier of Example 1.

[Examples 2-14, Comparative Examples 1-4]
Carriers were obtained in the same manner as in Example 1, except that the magnetic particles were changed according to Table 3.
And the obtained carrier was made into the carrier of each Examples 2-14 and Comparative Examples 1-4.

[Evaluation]
(Characteristic evaluation)
For the magnetic particles of the carrier obtained in each example, the volume particle size distribution (peak particle size, minimum particle size out of 2% frequency particle size, maximum particle size out of 2% frequency particle size), circularity, surface The average unevenness interval and the arithmetic surface roughness were examined by the method described above.
In Table 2, “A” is the peak particle size (μm) in the volume particle size distribution, and “B” is the minimum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution. “C” indicates the maximum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution.

(Actual machine evaluation)
The carrier obtained in each example and toner (to be described later) were mixed with a toner concentration of 9% by mass to obtain a developer.
The obtained developer. The developer was charged in a DCC400 remodeling machine (the toner density sensor was invalidated and the print speed was 70 sheets / min).
Then, 50 sheets of blank paper were printed on A4 paper in an environment of 30 ° C. and 88% RH, and the fog was visually evaluated.
Next, a halftone image having an image density of 30% was printed on A4 paper, and the color point and white point were visually evaluated.
Further, 10 sheets of a solid image (100% image density) of 10 cm square were printed on A4 paper, and the color difference (ΔE) between the first sheet and the tenth sheet was evaluated as an image quality evaluation.

The evaluation criteria are as follows.
Color point: No “◎”, 1 or less for “A” A4, 3 or less for “Δ” A4, 4 or more for “×” A4 • White point: No for “◎”, 1 for “O” A4 Less than 3 pieces, “△” A4 or less, “×” 4 pieces or more with A4 ・ Cover: No “◎”, “○” light color can be confirmed, “△” slight color can be confirmed, “×” A clear color can be confirmed. Image quality (color difference ΔE): “◎” ΔE ≦ 1, “◯” ΔE ≦ 1.3, “Δ” ΔE ≦ 1.8, “×” ΔE> 1.8

The color difference (ΔE) was measured with a reflection densitometer X-rite 939 (manufactured by X-rite).
The color difference (ΔE) is obtained by taking the square root of the square sum of the distance difference in the L * a * b * space in the CIE 1976 (L * a * b *) color system. The CIE 1976 (L * a * b *) color system is a color space recommended by the CIE (International Lighting Commission) in 1976, and is defined in “JIS Z 8729” in the Japanese Industrial Standards.

(toner)
The toner used for the developer produced in the actual machine evaluation is produced as follows.

-Preparation of colorant dispersion 1-
Cyan pigment: Copper phthalocyanine B15: 3 (Daiichi Seika): 50 parts by mass Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts by mass Ion-exchanged water: 200 parts by mass Dispersion was carried out for 5 minutes with an Ultra-Turrax manufactured by IKA and for 10 minutes with 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 by mass-Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 1 part by mass-Ion-exchanged water: 80 parts by mass The above is mixed in a heat-resistant container The mixture was 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 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 (manufactured by Wako Pure Chemical Industries, Ltd.): 30 parts by mass n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.): 10 parts by mass ・ β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.): 1.3 parts by mass / dodecanethiol (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 parts by mass--aqueous layer 1--
-Ion exchange water: 17 parts by mass-Anionic surfactant (Dowfax, manufactured by Dow Chemical): 0.4 part by mass--Aqueous layer 2--
-Ion exchange water: 40 parts by mass-Anionic surfactant (Dowfax, manufactured by Dow Chemical): 0.05 parts by mass-Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 parts by mass

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. 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-
-Resin dispersion 1: 150 parts by weight-Colorant dispersion 1: 30 parts by weight-Release agent dispersion 1: 40 parts by weight-Polyaluminum chloride: 0.4 parts by weight The above ingredients are IKE in a stainless steel flask. After thoroughly mixing and dispersing using an ultra turrax manufactured by the company, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After holding at 48 ° C. for 80 minutes, 70 parts by mass 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 particles.

  The volume average particle size of the toner particles is 6.2 μm, and the volume average particle size distribution index GSDv is 1.19. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135.

Next, the obtained toner particles are mixed with silica (SiO ₂ ) particles having a primary particle average particle size of 40 nm and surface-hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid, Add a metatitanic acid compound particle with an average primary particle diameter of 20 nm, which is a reaction product of isobutyltrimethoxysilane, so that the coverage of the toner particle surface is 40%, and mix with a Henschel mixer to obtain a toner. It was.

From the above results, it can be seen that in this example, better results were obtained for the evaluation of the color point, white point, fog, and image quality (color difference ΔE) than in the comparative example.
In particular, in the present example, compared to the comparative example, a better result is obtained regarding the evaluation of the color point, which indicates that the toner aggregation is suppressed.

1Y, 1M, 1C, 1K, 107 photoconductor (image carrier)
2Y, 2M, 2C, 2K, 108 Charging roller 3Y, 3M, 3C, 3K Laser beam 3, 110 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 Developer cartridge 10Y, 10M, 10C, 10K Unit 20 Intermediate transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer roller (transfer means)
28, 115 Fixing device (fixing means)
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 Recording paper (transfer object)

Claims (8)

Magnetic particles having a circularity of 0.950 or more and 0.990 or less and a volume particle size distribution satisfying the relationship of the following formula (1):
A coating resin layer that coats the magnetic particles;
An electrostatic charge developing carrier having:
Formula (1): 1.5 ≦ (C−A) / (A−B) ≦ 3.5
(In Formula (1), A shows the peak particle size (μm) in the volume particle size distribution. B shows the minimum particle size (μm) among the particle sizes having a frequency of 2% in the volume particle size distribution. (The maximum particle size (μm) is shown among the particle sizes having a frequency of 2% in the volume particle size distribution.)   The carrier for electrostatic charge development according to claim 1, wherein a peak particle size in a volume particle size distribution of the magnetic particles is 20 μm or more and 30 μm or less.   3. The electrostatic charge developing carrier according to claim 1, wherein the average irregularity interval Sm on the surface of the magnetic particle is 1.5 μm or more and 3.5 μm or less.   4. The electrostatic charge developing carrier according to claim 1, wherein the surface roughness Ra of the magnetic particles is 0.1 μm or more and 0.5 μm or less. 5.   An electrostatic charge developing developer comprising a toner and the electrostatic charge developing carrier according to claim 1. The developer for electrostatic charge development according to claim 5 is contained, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the developer for electrostatic charge development to form a toner image. With developing means,
A process cartridge that is detachable from the image forming apparatus. An electrostatic latent image carrier;
Charging means for charging the surface of the electrostatic latent image holding member;
Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrostatic latent image holding member;
An electrostatic charge developing developer according to claim 5 is accommodated, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the electrostatic charge developing developer to form a toner image. Developing means to form;
Transfer means for transferring the toner image to a recording medium;
Fixing means for fixing a toner image on the recording medium;
An image forming apparatus comprising: A charging step for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming step of forming an electrostatic charge image on the surface of the charged electrostatic latent image holding member;
A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member to form a toner image by the electrostatic charge developing developer according to claim 5;
A transfer step of transferring the toner image to a recording medium;
A fixing step of fixing a toner image on the recording medium;
An image forming method comprising: