JP7040262B2 - Developer set and image forming equipment - Google Patents

Description

The present invention relates to a developer set and an image forming apparatus.

In the electrophotographic method, an electrostatic charge image formed on the surface of an image holder (photoreceptor) is developed with a developer containing toner, the obtained toner image is transferred to a recording medium, and this is transferred by a thermal roll or the like. An image can be obtained by fixing.

Patent Document 1 describes "a carrier that constitutes a developer used in an image forming method for sequentially transferring toner images of a plurality of colors to form an image, and is a carrier coat in a carrier of a developer that first transfers a toner image. Carrier coat amount C2 to Cn (n indicates the total number of colors of the toner forming the image, and Cn is the carrier in the nth carrier of the developer that transfers the amount C1 in the carrier of each color to be transferred thereafter. A carrier characterized by being smaller than the coating amount.) ”Is disclosed.

Japanese Unexamined Patent Publication No. 2007-248972

As the developer applied to the image forming apparatus, a two-component developer containing toner and a carrier is used.
On the other hand, there is also known an image forming apparatus in which a plurality of image forming units are arranged along the traveling direction of the transferred body. For example, in an image forming apparatus in which the second image forming unit is arranged downstream of the first image forming unit in the traveling direction of the transferred body, the second image forming unit is formed on the transferred body by the first image forming unit. After the first toner image is transferred, the second toner image formed by the second image forming unit is superimposed and transferred.
Here, compared to the toner (excluding the black toner) contained in the developer (hereinafter, referred to as “first developer”) housed in the first image forming unit, the second image forming unit is used. When the dielectric loss rate of the toner contained in the contained developer (hereinafter referred to as "second developer") is high, and when the second toner image is superimposed and transferred, the first toner is transferred. The image sometimes collapsed. The collapse of the first toner image is reflected in the fixed image, and as a result, unevenness in image density may occur.

Further, when at least one of the specific gravity and the volume average particle size of the toner contained in the "second developer" is higher than that of the toner (excluding the black toner) contained in the "first developer". Similarly, the first toner image may be distorted, and as a result, uneven image density may occur.

The subject of the present invention is a developer set having a higher dielectric loss rate of the toner contained in the second developer than the toner contained in the first developer, or a first developer. In a developer set in which at least one of the specific gravity and the average particle size of the toner contained in the second developer is higher than that of the toner, the nitrogen-containing particles on the surface of the carrier contained in the first developer. A second image than the first image forming unit, as compared to the case where the content (N1) and the content (N2) of the nitrogen-containing particles on the surface of the carrier contained in the second developer are the same. It is an object of the present invention to provide a developer set in which unevenness in image density of a fixed image obtained by an image forming apparatus in which a forming unit is arranged on the downstream side in a traveling direction of a transfer target is suppressed.

The above problem is solved by the following means.

<1>
It has a first developer containing a first toner other than the black toner and a first carrier, and a second developer containing a second toner and a second carrier. The carrier and the second carrier include a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles, and the dielectric loss of the second toner as compared with the first toner. A developer set having a high rate and a high content (N1) of the nitrogen-containing particles on the surface of the first carrier as compared with the content (N2) of the nitrogen-containing particles on the surface of the second carrier.
<2>
It has a first developer containing a first toner other than the black toner and a first carrier, and a second developer containing a second toner and a second carrier. The carrier and the second carrier include a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles, and has a specific gravity of the second toner and a specific gravity of the second toner as compared with the first toner. At least one of the volume average particle diameters is high, and the content (N1) of the nitrogen-containing particles on the surface of the first carrier is higher than the content (N2) of the nitrogen-containing particles on the surface of the second carrier. High developer set.
<3>
The ratio of the content (N1) of the nitrogen-containing particles on the surface of the first carrier to the content (N2) of the nitrogen-containing particles on the surface of the second carrier is 1.10 <N1 / N2 <2. .. The developer set according to <1> or <2>, which satisfies 50.
<4>
The developer set according to <3>, wherein the ratio satisfies 1.6 <N1 / N2 <2.2.
<5>
The developer set according to any one of <1> to <4>, wherein the content (N1) of the nitrogen-containing particles on the surface of the first carrier satisfies 6.0 <N1 <8.0.
<6>
The developer set according to <5>, wherein the content (N1) of the nitrogen-containing particles on the surface of the first carrier satisfies 7.0 <N1 <7.8.
<7>
The developer set according to any one of <1> to <6>, wherein the nitrogen-containing particles have an average particle diameter of 100 nm or more and 800 nm or less.
<8>
The developer set according to <7>, wherein the nitrogen-containing particles have an average particle diameter of 300 nm or more and 500 nm or less.
<9>
The developer set according to any one of <1> to <8>, wherein the nitrogen-containing particles include at least one selected from the group consisting of melamine resin particles and benzoquanamine resin particles.
<10>
The developer set according to <9>, wherein the nitrogen-containing particles are melamine resin particles.
<11>
The first developer is a yellow developer containing yellow toner as the first toner, a magenta developer containing magenta toner as the first toner, and a cyan developer containing cyan toner as the first toner. The developer set according to any one of <1> to <10>, which comprises at least one selected from the group consisting of a clear developer containing clear toner as the first toner.
<12>
The second developer contains at least one of a white developer containing a white toner as the second toner and a brilliant developer containing a brilliant toner as the second toner <1> to <11>. The developer set according to any one of the above.
<13>
Of the developer set according to any one of <1> to <12>, the first image forming unit containing the first developer and any one of <1> to <12>. In the developer set according to the above, the second image forming unit containing the second developing agent is provided, and the first image forming unit and the second image forming unit run the transferred body. An image forming apparatus that is arranged along the direction and in which the second image forming unit is arranged downstream of the first image forming unit in the traveling direction of the transferred body.

According to the invention according to <1>
In a developer set in which the dielectric loss rate of the toner contained in the second developer is higher than that of the toner contained in the first developer, the nitrogen on the surface of the carrier contained in the first developer is used. Compared to the case where the content of the contained particles (N1) and the content of the nitrogen-containing particles on the surface of the carrier contained in the second developer (N2) are the same, the first image forming unit is higher than the first image forming unit. Provided is a developer set in which unevenness in image density of a fixed image obtained by an image forming apparatus in which the image forming unit 2 is arranged on the downstream side in the traveling direction of the transferred object is suppressed.
According to the invention according to <2>
In a developer set in which at least one of the specific gravity and the average particle size of the toner contained in the second developer is higher than that of the toner contained in the first developer, the first developer is contained. The first image is compared with the case where the content (N1) of the nitrogen-containing particles on the surface of the carrier and the content (N2) of the nitrogen-containing particles on the surface of the carrier contained in the second developer are the same. Provided is a developer set in which unevenness in image density of a fixed image obtained by an image forming apparatus in which a second image forming unit is arranged downstream of the forming unit in the traveling direction of the transferred object is suppressed.
According to the inventions according to <3> and <4>,
The ratio of the content (N1) of the nitrogen-containing particles on the surface of the first carrier to the content (N2) of the nitrogen-containing particles on the surface of the second carrier is 1.10 or less or 2.50 or more. Provided is a developer set in which unevenness in image density of the obtained fixed image is suppressed as compared with the case of.
According to the inventions of <5> and <6>,
Provided is a developer set in which unevenness in image density of the obtained fixed image is suppressed as compared with the case where the content (N1) of the nitrogen-containing particles on the surface of the first carrier is 6 or less or 8 or more. ..
According to the inventions of <7> and <8>,
Provided is a developer set in which unevenness in image density of the obtained fixed image is suppressed as compared with the case where the average particle size of the nitrogen-containing particles is less than 100 nm or more than 800 nm.
According to the inventions <9> to <12>,
Compared to the case where the content of nitrogen-containing particles (N1) on the surface of the first carrier and the content of nitrogen-containing particles (N2) on the surface of the second carrier are the same.
Provided is a developer set in which unevenness in image density of the obtained fixed image is suppressed.
According to the invention according to <13>
Compared to an image forming apparatus to which a developer set in which the content of nitrogen-containing particles (N1) on the surface of the first carrier and the content (N2) of nitrogen-containing particles on the surface of the second carrier are the same is applied. Provided is an image forming apparatus in which unevenness in image density of the obtained fixed image is suppressed.

It is a schematic block diagram which shows an example of the image forming apparatus of this embodiment. It is a schematic block diagram which shows an example of the process cartridge of this embodiment.

Hereinafter, embodiments of the invention will be described. These explanations and examples are illustrative of embodiments and do not limit the scope of the invention.

Hereinafter, the developer set of the present embodiment will be described with reference to two preferred embodiments ([first embodiment] and [second embodiment]). In addition, the above two embodiments are collectively referred to as "the present embodiment".

[First Embodiment]
The developer set of the first embodiment is a first developer containing a first toner other than black toner and a first carrier, and a second developer containing a second toner and a second carrier. The first carrier and the second carrier are provided with a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles, and the first toner has In comparison, the dielectric loss rate of the second toner is high, and the content of the nitrogen-containing particles on the surface of the first carrier is higher than the content of the nitrogen-containing particles (N2) on the surface of the second carrier. (N1) is high.

[Second Embodiment]
The developer set of the second embodiment is a first developer containing a first toner other than black toner and a first carrier, and a second developer containing a second toner and a second carrier. The first carrier and the second carrier are provided with a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles, and the first toner has In comparison, at least one of the specific gravity and the volume average particle diameter of the second toner is higher, and the content of the nitrogen-containing particles (N2) on the surface of the second carrier is higher than that of the surface of the first carrier. The content (N1) of the nitrogen-containing particles is high.

Both the developer sets of the first embodiment and the second embodiment have the above-mentioned configuration, so that the second image forming unit is arranged on the downstream side in the traveling direction of the transferred body with respect to the first image forming unit. A developer set in which unevenness in image density of a fixed image obtained by an image forming apparatus is suppressed can be obtained.
The reason is not clear, but it is presumed as follows.

In an image forming apparatus in which two image forming units are arranged downstream of the first image forming unit in the traveling direction of the transferred object, the first toner formed on the transferred object by the first image forming unit. After the image is transferred, the second toner image formed by the second image forming unit is superimposed and transferred. In the transfer of toner to the transfer target, triboelectric charging occurs due to the stirring between the toner and the carrier in the developing machine, and since the toner is charged, the toner is transferred to the transfer target due to the voltage difference applied in the transfer unit. It is done by.
At this time, it is contained in the second developer provided in the second image forming unit as compared with the first toner (excluding the black toner) contained in the first developer provided in the first image forming unit. The second is that the dielectric loss rate of the second toner is high, or at least one of the specific gravity and the volume average particle size of the second toner is higher than that of the first toner (excluding the black toner). When the toner image of No. 1 was transferred, the first toner image may be distorted.
This is because the second toner has at least a high dielectric loss rate, a high specific gravity, or a large diameter with respect to the first toner, and these properties are the first toner and the second toner. When the second toner image is overlaid on the first toner image and transferred, more load is applied to the first toner image in addition to the load of the nip pressure of the transfer portion, as compared with the case where the same is true. On the other hand, it is thought that this is due to this. Therefore, among the toners in the first toner image, those having a weak electrostatic adhesion to the transferred object are in an extruded state, the toner image is deformed, and the toners are rearranged with each other. When the first toner image is deformed or the toner is rearranged, the first toner image is displaced and may appear as density unevenness.
On the other hand, in the developer set according to the present embodiment, the content of nitrogen-containing particles (N1) on the surface of the first carrier is higher than the content of nitrogen-containing particles (N2) on the surface of the second carrier. high.
Here, since the nitrogen-containing particles are known to exhibit high positive chargeability, the presence of a large amount of nitrogen-containing particles in the surface layer covering the carrier improves the physical frictional force and imparts electrical charge. The force can be improved, the charge rising property is improved, sufficient charge can be obtained even with a small amount of stirring, and the charge distribution becomes uniform and narrow.
By adopting the above configuration of the developer set of the present embodiment, the first toner can be sufficiently charged even with a small amount of stirring, and the charge distribution becomes uniform and narrow, so that the electrostatic adhesion force with the transferred object is increased. The amount of low-charged toner, which is a weak toner, decreases.
Therefore, even when the second toner image is superimposed on the first toner image and transferred, it is considered that the first toner image is less likely to be distorted and the image density unevenness of the obtained fixed image is suppressed. ..

Hereinafter, the configuration of the developer set according to the above-mentioned first embodiment and the second embodiment (hereinafter, collectively referred to as “the present embodiment” for convenience) will be described in detail.

<Developer set>
The developer set according to the present embodiment includes a first developer containing a first toner other than black toner and a first carrier, a second developer containing a second toner and a second carrier, and a second developer. have.

The first developer is, for example, a yellow developer containing yellow toner as a first toner, a magenta developer containing magenta toner as a first toner, a cyan developer containing cyan toner as a first toner, and the above. As the first toner, at least one selected from the group consisting of a clear developer containing a clear toner corresponds.
The second developer corresponds to, for example, at least one of a white developer containing a white toner as the second toner and a brilliant developer containing a brilliant toner as the second toner.
That is, the first developer and the second developer may be one kind or a plurality of kinds, respectively.
Further, the developer according to the present embodiment may have other developer in addition to the first developer and the second developer. As the other developer, a black developer containing black toner may be used as the toner.

The mixing ratio (mass ratio) of the toner and the carrier in each developer varies depending on the type of toner and carrier used and is not particularly limited, but toner: carrier = 1: 100 to 30: 100 is preferable, and 3: 100 to 20: 100 is more preferable.

[Career]
Hereinafter, the details of the carriers (that is, the first carrier and the second carrier) used in the developer set according to the present embodiment will be described.
The first carrier and the second carrier include a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles.

(Magnetic core material)
Examples of the magnetic core material 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 dispersion type in which these particles are dispersed in a resin. Examples include resin particles. Further, examples of the magnetic core material include particles obtained by impregnating a porous magnetic powder with a resin.

The magnetic core material may be, for example, ferrite particles represented by the following formula.
-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 may contain at least Mn as the metal element.
M is mainly Mn, but is composed of Li, Ca, Sr, Sn, Cu, Zn, Ba, Mg, and Ti (preferably from Li, Ca, Sr, Mg, and Ti from the environmental point of view. At least one selected from the group) may be combined.

The magnetic core material is obtained by magnetic granulation and sintering, but as a pretreatment thereof, the magnetic material may be crushed. The crushing method is not particularly limited, and examples thereof include known crushing methods, and specific examples thereof include a mortar, a ball mill, and a jet mill.

Here, the resin contained in the dispersed resin particles or the like as the magnetic core material is not particularly limited, and for example, a styrene resin, an acrylic resin, a phenol resin, a melamine resin, an epoxy resin, or a urethane resin. , Polyester resin, silicone resin and the like. Further, the dispersed resin particles or the like as the magnetic core material may further contain other components such as a charge control agent and fluorine-containing particles, depending on the purpose.

The volume average particle size of the magnetic core material is, for example, preferably 10 μm or more and 500 μm or less, preferably 15 μm or more and 80 μm or less, and more preferably 20 μm or more and 60 μm or less.

The volume average particle size of the magnetic core material is measured by the following method.
The particle size distribution is measured using a laser diffraction / scattering particle size distribution measuring device (LS Particle Size Analogizer (Beckman-Coulter) measuring device. ISOTON-II (Beckman-Coulter) is used as the electrolytic solution. The number of particles to be measured is 50,000.
Then, for the measured particle size distribution, a cumulative distribution is drawn from the small diameter side with respect to the divided particle size range (channel), and the particle size (sometimes expressed as "D50v") that becomes a cumulative 50% is ". It is defined as "volume average particle size".
The volume average particle size of the carrier can be determined by performing the above measurement on the carrier obtained by separating the toner and the carrier by air blowing the developer in the developing apparatus.

(Coating resin layer)
The first carrier and the second carrier of the present embodiment are coated with a magnetic core material and include a coated resin layer containing nitrogen-containing particles.

Examples of the coating resin of the coating resin layer include acrylic resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacrylonitrile resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl chloride resin, polyvinyl carbazole resin, and polyvinyl ether. Resin, polyvinyl ketone resin, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, straight silicone resin having organosiloxane bond or its modified product, fluororesin, polyester resin, polyurethane resin, polycarbonate resin, phenol Examples thereof include resins, amino resins, amide resins, and epoxy resins.

Examples of the nitrogen-containing particles include melamine resin particles, benzoquanamine resin particles, urea resin particles, and urethane resin particles, and melamine resin particles or benzoquinamine resin are preferable from the viewpoint of suppressing uneven image density in the obtained fixed image.

Here, in the developer set of the present embodiment, the content (N1) of the nitrogen-containing particles on the surface of the first carrier is higher than the content (N2) of the nitrogen-containing particles on the surface of the second carrier. Since it is high, unevenness in image density of the obtained fixed image is suppressed.
Further, from the viewpoint of suppressing unevenness in the image density of the obtained fixed image, the content (N1) of the nitrogen-containing particles on the surface of the first carrier is relative to the content (N2) of the nitrogen-containing particles on the surface of the second carrier. The ratio is preferably 1.10 <N1 / N2 <2.50, more preferably 1.60 <N1 / N2 <2.2.
Similarly, from the viewpoint of suppressing uneven image density of the obtained fixed image, the content (N1) on the surface of the first carrier is preferably 6.0 <N1 <8.0, preferably 7.0. It is more preferable that <N1 <7.8.

Here, the content of the nitrogen-containing particles on the surface of the carrier indicates the content ratio of the element N contained in the nitrogen-containing particles to the total of the element C and the element О contained in the coating resin covering the carrier. ..
The content ratio of element N contained in nitrogen-containing particles to the total of element C and element О contained in the coating resin can be measured by using an X-ray photoelectron spectrometer (XPS), and is measured by the following method. ..
Element N, element C, and element О are evaluated by an XPS element analyzer every 150 nm from the carrier surface toward the center of the carrier to a depth of 600 nm, and nitrogen is contained in the total of element C and element О contained in the coating resin. The content ratio of the element N contained in the particles is defined as "content of nitrogen-containing particles on the surface of the carrier (atom%)".
The measurement conditions are as follows.
・ Analytical device: JPS-9000MX manufactured by JEOL Ltd.
・ X-ray source: MgKα ray ・ Acceleration voltage: 10kV
・ Emission current: The value obtained by setting it to 30 mA.

For the distinction between the element N contained in the nitrogen-containing particles and the element N contained in the components other than the nitrogen-containing particles (coated resin layer, etc.) including the resin layer, the measured elemental analysis results should be peak-separated. Can be determined by.
Also, regarding the distinction between the element C and element О contained in the coated resin layer and the element C and element О contained in components other than the coated resin (nitrogen-containing particles, etc.), the measured elemental analysis results are peak-separated. It can be discriminated by.

The nitrogen-containing particles are partially exposed on the surface of the coated resin layer. However, even if the exposure amount of the nitrogen-containing particles is small before the coating resin layer is worn, the exposure amount of the nitrogen-containing particles increases due to the wear of the coating resin layer over time, and the charging ability is exhibited. It will be.
The content of nitrogen-containing particles on the surface of the carrier is the content before the coating resin layer is worn (that is, the content of nitrogen-containing particles on the surface of the carrier equivalent to that of a new product).

The average particle size of the nitrogen-containing particles is preferably 100 nm or more and 800 nm or less, and more preferably 300 nm or more and 500 nm or less, from the viewpoint of suppressing unevenness in the image density of the obtained fixed image.

For the average particle size of the nitrogen-containing particles, the nitrogen-containing particles are separated from the layer, 100 primary particles of the nitrogen-containing particles are observed with a SEM (Scanning Electron Microscope) device at a magnification of 40,000 times, and image analysis of the primary particles is performed. Measure the equivalent circle diameter of each particle. The 50% diameter (D50v) in the cumulative frequency of the volume-based equivalent circle diameter obtained is obtained, and this is measured as the average particle diameter (volume average particle diameter) of the nitrogen-containing particles.

The coated resin layer may contain resin particles other than the nitrogen-containing particles described above for the purpose of controlling charge, conductive particles for the purpose of controlling resistance, and the like. The coating layer may contain other additives.
The resin particles are not particularly limited, but those having charge control-imparting properties are preferable, and examples thereof include polyester resin particles and acrylic resin particles.
Examples of the conductive particles include carbon black, various metal powders, and metal oxides (for example, titanium oxide, tin oxide, magnetite, ferrite, etc.). These may be used alone or in combination of two or more. Among these, carbon black particles are preferable in terms of good manufacturing stability, cost, conductivity and the like. The type of carbon black is not particularly limited, but carbon black having a DBP oil absorption of 50 ml / 100 g or more and 250 ml / 100 g or less is preferable because of its excellent production stability.

When the coating resin layer contains conductive particles, the content of the conductive particles in the coating resin layer is, for example, 0.1% by mass or more and 50% by mass or less, and 0.15% by mass or more and 20% by mass or less. Is preferable, and 0.2% by mass or more and 10% by mass or less is more preferable.

The coating amount of the coating resin layer is, for example, 0.5% by mass or more (preferably 0.7% by mass or more and 6.0% by mass) with respect to the total mass of the carriers in both the first carrier and the second carrier. % Or less, more preferably 1.0% by mass or more and 5.0% by mass or less).

The coating amount of the coating resin layer is obtained as follows.
In the case of a solvent-soluble coated resin layer, the concentrated carrier is dissolved in a solvent capable of dissolving the coated resin layer (for example, toluene, N-methylpyrrolidone, etc.), and the magnetic core material is held by a magnet and coated. Rinse off the solution in which the resin layer is dissolved. By repeating this several times, the magnetic core material from which the coating resin layer has been removed remains. The coating amount is calculated by drying, measuring the mass of the magnetic core material, and dividing the difference by the carrier amount.
Specifically, 20.0 g of the carrier is weighed, placed in a beaker, 100 g of toluene is added, and the mixture is stirred with a stirring blade for 10 minutes. Place a magnet on the bottom of the beaker and let toluene flow so that the magnetic core material does not flow out. This is repeated 4 times to dry the beaker after rinsing. The amount of magnetic powder after drying is measured, and the coating amount is calculated by the formula [(carrier amount-magnetic core material amount after cleaning) / carrier amount].
On the other hand, in the case of a solvent-insoluble coating layer, a Thermo plus EVOII differential thermal balance TG820 manufactured by Rigaku Co., Ltd. is used to heat the layer in a nitrogen atmosphere at room temperature (25 ° C) or higher and 1000 ° C or lower to reduce its mass. The resin coating amount is calculated from.

The method for forming the coating resin layer on the surface of the magnetic core material is not particularly limited, and a conventionally known method is adopted. For example, a dipping method in which a solution for forming a coated resin layer is prepared and a magnetic core material is immersed in the solution for forming a coated resin layer to coat it; a spray method in which the solution for forming a coated resin layer is sprayed on the surface of the magnetic core material; Flow bed method in which the solution for forming the coating resin layer is sprayed while the magnetic core material is suspended by flowing air; the magnetic core material and the solution for forming the coating resin layer are mixed in a kneader coater, and then the solvent is removed. A kneader coater method; for example, a powder coating method in which a magnetic core material and a resin powder are heated and mixed together; and the like can be mentioned. Further, after forming the coating resin layer, heat treatment may be performed by an apparatus such as an electric furnace or a kiln.

-Other characteristics of the carrier-
As for the magnetic force of the carrier, the saturation magnetization in a magnetic field of 1000 oersted may be, for example, 40 emu / g or more, or 50 emu / g or more.
Here, the saturation magnetization of the carrier is measured using a vibration sample type magnetic measuring device VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.). The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the device. The measurement is performed by applying an applied magnetic field and sweeping up to 3000 oersted. Next, the applied magnetic field is reduced to create a hysteresis curve on the recording paper. Obtain the saturation magnetization from the curve data.

-Volume average particle size of carriers-
The carriers (that is, the first carrier and the second carrier) used in the developer set according to the present embodiment preferably have a volume average particle size of 20 μm or more and 100 μm or less. The volume average particle size of the second carrier is larger than the volume average particle size of the first carrier.
Here, the volume average particle size of the carrier is measured by the following method. The same applies to the measurement of the volume average particle size of the magnetic core material.
The particle size distribution is measured using a laser diffraction / scattering particle size distribution measuring device (LS Particle Size Analogizer (Beckman-Coulter) measuring device. ISOTON-II (Beckman-Coulter) is used as the electrolytic solution. The number of particles to be measured is 50,000.
Then, for the measured particle size distribution, a cumulative distribution is drawn from the small diameter side with respect to the divided particle size range (channel), and the particle size (sometimes expressed as "D50v") that becomes a cumulative 50% is ". It is defined as "volume average particle size".
The volume average particle size of the carrier can be determined by performing the above measurement on the carrier obtained by separating the toner and the carrier by air blowing the developer in the developing apparatus.

[toner]
As described above, the first toner of the present embodiment is a toner other than the black toner, and corresponds to at least one selected from the group including, for example, yellow toner, magenta toner, cyan toner, and clear toner. The first toner of the present embodiment also corresponds to a neutral color toner other than yellow toner, magenta toner, and cyan toner.
The second toner of the present embodiment corresponds to at least one selected from the group including, for example, a white toner and a brilliant toner.
In the present embodiment, in addition to the first toner and the second toner, black toner may be further used.

-Toner dielectric loss rate-
The dielectric loss rate of the toner is higher in the second toner than in the first toner.
The dielectric loss rate of the toner varies depending on the composition of the toner and the dispersed state of the colorant. Among them, the dielectric loss rate of the toner is particularly easily affected by the type of the colorant used. For example, the brilliant toner using a brilliant pigment as a colorant and the white toner using a white pigment as a colorant are other toners (for example, yellow toner, magenta toner, cyan toner, black toner, clear toner, etc.). The dielectric loss rate tends to be larger than that of.

Here, the dielectric loss rate of the toner will be described. First, the dielectric constant tangent (tan δ) is expressed by the ratio of the real part ε'and the imaginary part ε "at the complex permittivity ε = ε'-iε" (i is an imaginary unit), and the dielectric tangent (tan δ) = ε. It is represented by "/ ε'. Of these, the imaginary part ε" is called the permittivity.
The dielectric loss rate of the toner is determined by, for example, pellet molding (diameter 50 mm) of 5 g of the toner to be measured with a pressure molding machine, seasoning treatment in an environment of 28 ° C. and 85% RH for 17 hours, and then an LCR meter (LCR meter). 6440A type: manufactured by Toyo Technica Co., Ltd.) can be obtained by measuring under the conditions of a frequency of 1 kHz and a voltage of 5 V in an environment of 28 ° C. and 85% RH.

The dielectric loss rate of the second toner is preferably 1.5 times or more and 6.0 times or less, more preferably 1.8 times or more and 5.0 times or less, and 2.0 times or less the dielectric loss rate of the first toner. The above 3.7 times or less is more preferable.
The dielectric loss ratio of the second toner is preferably 30 × 10 ^-3 or more and 70 × 10 ^-3 or less, more preferably 40 × 10 ^-3 or more and 65 × 10 ^-3 or less, and 45 × 10 ^-3 or more and 65. × 10 ^-3 or less is more preferable.
When the developer set has a plurality of first developers, it is preferable that the above-mentioned preferable range is applied to all of the plurality of first toners.

-Toner specific density-
The specific gravity of the toner varies depending on the type of pigment used in the toner and the amount of the pigment, but it is easily affected by the type of pigment. The average particle size of the toner can be controlled to a certain size (about 3.5 μm) or more in the manufacturing process.
The specific gravity or the average particle size of the toner is higher than that of the first toner at least one of the specific gravity and the average particle size of the second toner.

The specific gravity of the first toner is preferably 1.00 or more and 1.15 or less, and more preferably 1.07 or more and 1.13 or less. The specific gravity of the second toner is preferably 1.00 or more and 2.00 or less, and more preferably 1.16 or more and 1.70 or less.

The specific gravity of the toner is measured by the following measuring method.
Using a Le Chatelier specific gravity bottle, the specific gravity is adjusted by the following work in accordance with 5-2-1 of JIS-K-0061 (2001).
(1) Put 250 ml of ethyl alcohol in the Le Chatelier's specific gravity bottle and adjust so that the meniscus is at the scale position.
(2) Immerse the density bottle in a constant temperature water tank, and when the liquid temperature reaches 20.0 ± 0.2 ° C, accurately read the position of the meniscus on the scale of the density bottle (accuracy 0.0025 ml).
(3) Weigh 100 g of the sample.
(4) Place the weighed sample in a specific density bottle and remove bubbles.
(5) Immerse the density bottle in a constant temperature bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C, accurately read the position of the meniscus on the scale of the density bottle (accuracy 0.0025 ml).
(6) Calculate the specific density by the following formula.
-Formula: D = W / (L2-L1)
-Formula: S = D / 0.9982
In the formula, D is the density of the sample (g / cm ³ , 20 ° C.), S is the specific gravity of the sample (20 ° C.), W is the apparent mass of the sample (g), and L1 is the meniscus before the sample is placed in the specific gravity bottle. (Ml, 20 ° C.), L2 is the reading value of Meniscus after placing the sample in a specific gravity bottle (ml, 20 ° C.), and 0.9982 is the density of water at 20 ° C. (g / cm ³ ). ..

-Volume average particle size of toner-
The volume average particle size of the first toner is preferably 4.0 μm or more and 6.5 μm or less, and more preferably 4.5 μm or more and 6.0 μm or less. The average particle size of the second toner is preferably 5.0 μm or more and 15.0 μm or less, and more preferably 5.0 μm or more and 12.0 μm or less.

The volume average particle size of the toner is measured using Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolytic solution is measured using ISOTON-II (manufactured by Beckman Coulter).
At the time of measurement, 0.5 mg or more and 50 mg or less of the measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This is added to 100 ml or more and 50 ml or less of the electrolytic solution.
The electrolytic solution in which the sample is suspended is dispersed for 1 minute with an ultrasonic disperser, and the particle size distribution of particles having a particle size in the range of 2 μm or more and 60 μm or less is obtained by using an aperture with an aperture diameter of 100 μm by the Coulter Multisizer II. Measure. The number of particles to be sampled is 50,000.
A cumulative distribution is drawn from the small diameter side for the volume divided with respect to the particle size range (channel) divided based on the measured particle size distribution, and the particle size having a cumulative total of 50% is defined as the volume average particle size D50v.

Hereinafter, the first toner and the second toner will be described in detail.
First, general toners preferably used as a first toner other than black toner, such as yellow toner, magenta toner, and cyan toner, will be described, but black toner used as other toner will also be described below. It has the same configuration as a general toner.

The toner is composed of toner particles and, if necessary, an external additive.

(Toner particles)
The toner particles are composed of, for example, a binder resin, a colorant, a mold release agent, and other additives, if necessary.

-Bound resin-
Examples of the binder resin include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth) acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, etc.). N-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (eg, 2-ethylhexyl methacrylate) , Acrylonitrile, methacrylonitrile, etc.), Vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), Vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene, propylene) , Butacon, etc.), or a vinyl-based resin composed of a copolymer obtained by combining two or more of these monomers.
Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosins, mixtures of these with the vinyl resins, or these. Examples thereof include a graft polymer obtained by polymerizing a vinyl-based monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

The content of the binder resin is, for example, preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and 60% by mass or more and 85% by mass or less with respect to the entire toner particles. More preferred.

-Colorant-
Examples of colorants include carbon black, chrome yellow, Hansa yellow, benzine yellow, slene yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolon orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, and brilliant. Carmin 6B, Dupont Oil Red, Pyrazolon Red, Lissole Red, Rhodamin B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultra Marine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Various pigments such as malakite green oxalate, aclysine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindico-based, dioxazine-based, thiazine-based, azomethine-based, indico-based, phthalocyanine-based, aniline black Various dyes such as system, polymethine system, triphenylmethane system, diphenylmethane system, thiazole system and the like can be mentioned.
The colorant may be used alone or in combination of two or more.

As the colorant, a surface-treated colorant may be used or may be used in combination with a dispersant, if necessary. Further, a plurality of kinds of colorants may be used in combination.

The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less with respect to the entire toner particles.

-Release agent-
Examples of the release agent include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester waxes such as fatty acid esters and montanic acid esters. ; And so on. The release agent is not limited to this.

The melting temperature of the release agent is preferably 50 ° C. or higher and 110 ° C. or lower, and more preferably 60 ° C. or higher and 100 ° C. or lower.
The melting temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC) by the "melting peak temperature" described in the method for determining the melting temperature in JIS K 7121-1987 "Method for measuring the transition temperature of plastics". ..

The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less with respect to the entire toner particles.

-Other additives-
Examples of other additives include well-known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as an internal additive.

-Characteristics of toner particles-
The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core portion (core particles) and a coating layer (shell layer) covering the core portion. You may.
Here, the toner particles having a core-shell structure include, for example, a core portion composed of a binder resin and, if necessary, other additives such as a colorant and a mold release agent, and a binder resin. It is preferable that it is composed of a coated layer and.

The average circularity of the toner particles is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

The average circularity of the toner particles is obtained by (circumferential peripheral length) / (peripheral length) [(circumferential length of a circle having the same projected area as the particle image) / (peripheral length of the particle projected image)]. Specifically, it is a value measured by the following method.
First, a flow-type particle image analyzer (Sysmex) that captures a particle image as a still image by sucking and collecting toner particles to be measured, forming a flat flow, and instantly emitting strobe light, and analyzing the particle image. Obtained by FPIA-3000) manufactured by the company. The number of samplings for obtaining the average circularity is set to 3500.
When the toner has an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additive has been removed. ..

(External agent)
Examples of the external additive include inorganic particles. As the inorganic particles, SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ , CaO. _Examples thereof include SiO ₂ , K ₂ O · (TiO ₂ ) n, Al ₂ O 3.2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , _Л4 and the like.

The surface of the inorganic particles as an external additive should be hydrophobized. The hydrophobizing treatment is performed, for example, by immersing the inorganic particles in the hydrophobizing agent. The hydrophobizing agent is not particularly limited, and examples thereof include a silane-based coupling agent, a silicone oil, a titanate-based coupling agent, and an aluminum-based coupling agent. These may be used alone or in combination of two or more.
The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

Examples of the external additive include resin particles (resin particles such as polystyrene, polymethylmethacrylate (PMMA), and melamine resin), cleaning active agents (for example, metal salts of higher fatty acids typified by zinc stearate, and fluoropolymers). Particles) and the like.

The amount of the external additive added is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less with respect to the toner particles.

(Toner manufacturing method)
Next, a method for manufacturing the toner will be described.
Toner can be obtained by externally adding an external additive to the toner particles after manufacturing the toner particles.

The toner particles may be produced by any of a dry production method (for example, a kneading and pulverizing method, etc.) and a wet production method (for example, an agglomeration coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). The manufacturing method of the toner particles is not particularly limited to these manufacturing methods, and a well-known manufacturing method is adopted.
Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

Specifically, for example, when the toner particles are produced by the aggregation and coalescence method,
A step of preparing a resin particle dispersion liquid in which resin particles to be a binding resin are dispersed (resin particle dispersion liquid preparation step) and a step in the resin particle dispersion liquid (after mixing other particle dispersion liquids as necessary). (In the dispersion liquid), the step of aggregating the resin particles (other particles if necessary) to form the agglomerated particles (aggregated particle forming step), and the step of heating the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed. The toner particles are manufactured through the steps of fusing and coalescing the agglomerated particles to form the toner particles (fusing and coalescing step).

After obtaining the agglomerated particle dispersion liquid in which the agglomerated particles are dispersed, the agglomerated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed, and the resin particles are further added to the surface of the agglomerated particles. The step of agglomerating so as to adhere to form the second agglomerated particles and the second agglomerated particle dispersion liquid in which the second agglomerated particles are dispersed are heated to fuse and unite the second agglomerated particles. , Toner particles may be produced through the steps of forming toner particles having a core / shell structure.

Here, after the fusion / union step is completed, the toner particles formed in the solution are subjected to a known cleaning step, solid-liquid separation step, and drying step to obtain toner particles in a dried state.
In the cleaning step, it is preferable to sufficiently perform replacement cleaning with ion-exchanged water from the viewpoint of chargeability. The solid-liquid separation step is not particularly limited, but suction filtration, pressure filtration and the like may be performed from the viewpoint of productivity. The drying step is also not particularly limited, but from the viewpoint of productivity, freeze-drying, air-flow drying, flow-drying, vibration-type flow-drying and the like may be performed.

Then, the toner is produced, for example, by adding an external additive to the obtained dry toner particles and mixing them. The mixing may be performed by, for example, a V blender, a Henschel mixer, a Ladyge mixer or the like. Further, if necessary, coarse particles of toner may be removed by using a vibration sieving machine, a wind sieving machine, or the like.

(Clear toner)
Next, a clear toner (hereinafter, also referred to as “transparent toner”) preferably used as the first toner will be described.
The transparent toner includes transparent toner particles that do not contain a colorant or have a colorant content of 1.0% by mass or less of the toner particles.
Examples of the transparent toner include toners having transparent toner particles and an external additive. The transparent toner particles may contain a mold release agent and other additives, if necessary.
The content of the colorant in the entire transparent toner particles of the transparent toner is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and most preferably no colorant.
Since the binder resin, the external additive, the mold release agent, and other additives are the same as the above-mentioned toner (that is, the yellow toner used as the first toner, etc.), the description thereof will be omitted. Other matters similar to those of the above-mentioned toner will be omitted.

(Glowing toner)
Next, a brilliant toner suitably used as the second toner will be described.
Examples of the brilliant toner include a toner having brilliant toner particles containing a flat brilliant pigment and a binder resin, and an external additive. The glittering toner particles may contain a release agent, a colorant other than the glittering pigment, and other additives, if necessary.
Since the binder resin, the external additive, the release agent, the colorant other than the bright pigment, and other additives are the same as those of the above-mentioned toner (that is, the yellow toner used as the first toner, etc.). The explanation is omitted. Other matters similar to those of the above-mentioned toner will be omitted.

-Bright pigment-
Examples of the brilliant pigment include pigments (brilliant pigments) that can impart a brilliant feeling such as metallic luster. Specific examples of the glittering pigment include metal powders such as aluminum (metal of Al alone), brass, bronze, nickel, stainless steel, and zinc; mica coated with titanium oxide, yellow iron oxide, and the like; barium sulfate, layered Kay. Coated flaky inorganic crystal substrate such as acid salt and silicate of layered aluminum; Elementary crystal plate-shaped titanium oxide; Basic carbonate; Bismus acid oxychloride; Natural guanine; Fragmented glass powder; Metal-deposited flaky glass There is no particular limitation as long as it has a brilliant property such as powder.
Among the bright pigments, metal powder is preferable, and aluminum is most preferable, particularly from the viewpoint of specular reflection intensity.

Examples of the shape of the brilliant pigment include a flat shape (scale shape).
The average length of the brilliant pigment in the major axis direction is preferably 1 μm or more and 30 μm or less, more preferably 3 μm or more and 20 μm or less, and further preferably 5 μm or more and 15 μm or less.
The ratio (aspect ratio) of the average length in the major axis direction when the average length in the thickness direction of the brilliant pigment is 1, is preferably 5 or more and 200 or less, more preferably 10 or more and 100 or less, and 30 More than 70 or less is more preferable.

Each average length and aspect ratio of the brilliant pigment is measured by the following method. Using a scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Co., Ltd.), a photograph of the pigment particles was taken at a measurable magnification (300 to 100,000 times), and the obtained image of the pigment particles was taken in two dimensions. In this state, the length in the major axis direction and the length in the thickness direction of each particle are measured, and the average length and aspect ratio in the major axis direction of the bright pigment are calculated.

The content of the brilliant pigment is, for example, preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 15 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the brilliant toner particles.

-Characteristics of brilliant toner particles-
The toner particles may be brilliant toner particles having a single layer structure, or may be brilliant in a so-called core-shell structure composed of a core portion (core particles) and a coating layer (shell layer) covering the core portion. It may be toner particles.
The brilliant toner particles having a core-shell structure are composed of, for example, a core containing a brilliant pigment, a binder resin, and other additives such as a mold release agent, and a coating layer containing a binder resin. It should be configured.

-Average maximum thickness C and average circle equivalent diameter D of brilliant toner particles
It is preferable that the brilliant toner particles are flat and have an average circle equivalent diameter D longer than the average maximum thickness C. The ratio (C / D) of the average maximum thickness C to the average circle equivalent diameter D is more preferably in the range of 0.001 or more and 0.500 or less, and further in the range of 0.010 or more and 0.200 or less. The range of 0.050 or more and 0.100 or less is particularly preferable.
When the ratio (C / D) is 0.001 or more, the strength of the brilliant toner is ensured, fracture due to stress during image formation is suppressed, and the charge is reduced due to the exposure of the pigment, resulting in the occurrence. Fog is suppressed. On the other hand, when it is 0.500 or less, excellent brilliance can be obtained.

The average maximum thickness C and the average circle equivalent diameter D are measured by the following methods.
Glittering toner particles are placed on a smooth surface and vibrated to disperse them evenly. About 1000 brilliant toner particles, the maximum thickness C of the brilliant toner particles and the equivalent circle diameter D of the surface seen from above were magnified 1000 times by the color laser microscope "VK-9700" (manufactured by KEYENCE). Is measured and calculated by calculating the arithmetic mean value of them.

Angle between the long axis direction and the long axis direction of the brilliant pigment in the cross section of the brilliant toner particles When observing the cross section in the thickness direction of the brilliant toner particles, the long axis direction in the cross section of the brilliant toner particles. It is preferable that the ratio (number basis) of the brilliant pigment in which the angle between the brilliant pigment and the major axis direction is in the range of -30 ° to + 30 ° is 60% or more of the total brilliant pigments observed. .. Further, the above ratio is more preferably 70% or more and 95% or less, and particularly preferably 80% or more and 90% or less.
When the above ratio is 60% or more, excellent brilliance can be obtained.

Here, a method of observing the cross section of the brilliant toner particles will be described.
After embedding the glittering toner particles with a bisphenol A type liquid epoxy resin and a curing agent, a sample for cutting is prepared. Next, a cutting machine using a diamond knife, for example, an ultramicrotome device (UltracutUCT, manufactured by Leica) is used to cut the cutting sample at −100 ° C. to prepare an observation sample. The observation sample is observed with an ultra-high resolution field emission scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation) at a magnification in which about 1 to 10 bright toner particles can be seen in one field of view.
Specifically, the cross section of the brilliant toner particles (cross section along the thickness direction of the toner particles) is observed, and for the observed 100 toner particles, the long axis direction and the brilliant pigment in the cross section of the brilliant toner particles. The number of brilliant pigments whose angle with the major axis direction is in the range of -30 ° to + 30 ° can be determined by image analysis software such as image analysis software (WinROOF) manufactured by Mitani Shoji Co., Ltd. or an output sample of observation images. And count using a divider to calculate the ratio.

The "long-axis direction in the cross section of the brilliant toner particles" represents a direction orthogonal to the thickness direction of the brilliant toner particles having an average circle equivalent diameter D longer than the above-mentioned average maximum thickness C, and also "brilliant". The "long-axis direction of the sex pigment" represents the length direction of the bright pigment.

-Volume average particle size of the brilliant toner particles The volume average particle size of the brilliant toner particles is preferably 1 μm or more and 30 μm or less, and more preferably 3 μm or more and 20 μm or less.

(White toner)
Next, a white toner suitably used as the second toner will be described.
Examples of the white toner include toners containing white toner particles containing a white pigment and a binder resin, and an external additive. The white toner particles may contain a mold release agent and other additives, if necessary.
Since the binder resin, the external additive, the mold release agent, and other additives are the same as the above-mentioned toner (that is, the yellow toner used as the first toner, etc.), the description thereof will be omitted. Other matters similar to those of the above-mentioned toner will be omitted.

-White pigment-
The white pigment is not particularly limited as long as it is white, and is, for example, an inorganic pigment (for example, titanium oxide, barium sulfate, lead oxide, zinc oxide, lead titanate, potassium titanate, barium titanate, strontium titanate). , Zirconia, antimony trioxide, lead white, zinc sulfide, barium carbonate, etc.), organic pigments (eg, polystyrene resin, ureaformalin resin, polyacrylic resin, polystyrene / acrylic resin, polystyrene / butadiene resin, alkylbismelamine resin, etc.) And so on.
Further, a pigment having a hollow structure may be used. Examples of the pigment having a hollow structure include hollow inorganic pigments (for example, hollow silica, hollow titanium oxide, hollow calcium carbonate, hollow zinc oxide, zinc oxide tube particles, etc.) and hollow organic particles (styrene resin, acrylic resin, styrene / acrylic resin). , Styrene / acrylic acid ester / acrylic acid resin, styrene / butadiene resin, styrene / methyl methacrylate / butadiene resin, ethylene / vinyl acetate resin, acrylic acid / vinyl acetate resin, acrylic acid / maleic acid resin, etc.).
Furthermore, heavy calcium carbonate, light calcium carbonate, aluminum hydroxide, satin white, talc, calcium sulfate, magnesium oxide, magnesium carbonate, amorphous silica, colloidal silica, white carbon, kaolin, calcined kaolin, delaminated kaolin, aluminokei. Examples thereof include acid salt, sericite, bentonite, and smectite.
Among these, titanium oxide and zinc oxide are preferable as the white pigment.
The white pigment may be used alone or in combination of two or more.

As the white pigment, a surface-treated white pigment may be used, if necessary, or may be used in combination with a dispersant.

The content of the white pigment is, for example, preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the white toner particles. When the content of the white pigment is 10 parts by mass or more, whiteness and concealment are easily exhibited. On the other hand, when the content of the white pigment is 50 parts by mass or less, the interface between the white pigment and the binder resin does not increase more than necessary, so that the white toner image is less likely to be destroyed and the effect of suppressing image destruction is likely to be improved. ..
The content of the white pigment is preferably 20 parts by mass or more and 50 parts by mass or less, and more preferably 25 parts by mass or more and 45 parts by mass or less with respect to 100 parts by mass of the white toner particles.

The number average particle size of the white pigment is, for example, 200 nm or more and 400 nm or less. When the number average particle size of the white pigment is 200 nm or more and 400 nm or less, high whiteness and concealment are exhibited. The number average particle size of the white pigment is preferably 250 nm or more and 400 nm or less, and more preferably 250 nm or more and 350 nm or less.

The particle size distribution of the white pigment in the toner particles is calculated, for example, as follows.
After the white toner is mixed with the epoxy resin, embedded and solidified by being left to stand overnight, a thin piece having a thickness of 250 nm or more and 450 nm or less is prepared by using an ultramicrotome device (UltracutUCT, manufactured by Leica).
The obtained flakes are observed with an ultra-high resolution field emission scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation) to confirm the white pigment inside the toner particles.
The observed photograph is digitized and incorporated into image analysis software (Win ROOF) manufactured by Mitani Shoji Co., Ltd., and the number average particle size of the white pigment in the toner particles is obtained.

<Image forming device and image forming method>
An image forming apparatus and an image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes a first image forming unit and a second image forming unit arranged downstream of the first image forming unit in the traveling direction of the transferred body. There is.
Hereinafter, the image forming unit is also simply referred to as a “unit”. Further, the downstream side in the traveling direction of the transferred body is also simply referred to as "downstream side", and the upstream side in the traveling direction of the transferred body is also simply referred to as "upstream side".
The first unit has a first image holder and a first developing means for developing a static charge image formed on the surface of the first image holder as a toner image with a first developer. ..
The second unit has a second image holder and a second developing means for developing an electrostatic charge image formed on the surface of the second image holder as a toner image with a second developer. ..
The first developing means includes a first developer containing a first toner and a first carrier, and the second developing means contains a second toner and a second carrier. Each of the two developing agents is contained.
Further, the image forming apparatus according to the present embodiment includes a first transfer means for transferring the toner image formed on the surface of the first image holder by the first developing means to the transferred object, and a second developing means. The means comprises a second transfer means for transferring the toner image formed on the surface of the second image holder to the transferred object to which the first toner image is transferred.

Further, in the image forming method according to the present embodiment, in the first unit, a first electrostatic charge image is formed on the surface of the first image holder, and the first toner and the first carrier are included. In the first image forming step of developing the first electrostatic charge image as the first toner image and transferring the first toner image to the transferred object, and in the second unit, the second image. A second electrostatic charge image is formed on the surface of the retainer, and the second electrostatic charge image is developed as a second toner image by a second developer containing a second toner and a second carrier. It has a second image forming step of transferring the second toner image to the transferred object to which the toner image of the above is transferred.

Here, the "image forming unit" is an image forming means provided with at least an image holding body and a developing means, and the image forming unit also cleans the charging means, the electrostatic charge image forming means, and the image holding body. It may be provided with at least one selected from the cleaning members to be used.

The "transferred body" is a medium on which a toner image formed on the surface of an image holder is transferred. For example, in the case of a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image holder to a recording medium, the transferred body is a recording medium. Further, an intermediate transfer type apparatus in which the toner image formed on the surface of the image holder is primaryly transferred to the surface of the intermediate transfer body, and the toner image transferred to the surface of the intermediate transfer body is secondarily transferred to the surface of the recording medium. In the case of, the transcribed body becomes an intermediate transcribed body.

Further, the second unit "arranged on the downstream side in the traveling direction of the transferred body from the first image forming unit" is the second unit among the plurality of units arranged along the traveling direction of the transferred body. It is a unit arranged on the downstream side of the unit of 1.
In the present embodiment, the first unit may be one or a plurality. Further, in the image forming apparatus provided with a plurality of the first units, the first transfer means is also provided in the same number as the number of the first units. The second unit may also be one or a plurality. Further, in the image forming apparatus provided with a plurality of second units, the second transfer means is also provided in the same number as the number of the second units.
Further, the image forming apparatus is arranged in a unit other than the first unit and the second unit (for example, a unit arranged on the upstream side of the first unit and a unit arranged on the downstream side of the second unit). It may be equipped with a unit, etc.).

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image holder to a recording medium; an intermediate transfer body is a toner image formed on the surface of the image holder. An intermediate transfer type device that first transfers the toner image to the surface of the intermediate transfer body and then secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium; after the transfer of the toner image, the surface of the image holder before charging is cleaned. A well-known image forming device such as a device provided with a static elimination means for irradiating the surface of the image holder with static elimination light after the transfer of the toner image and before charging is applied.
In the case of an intermediate transfer type device, an intermediate transfer body in which a toner image is transferred to the surface, a primary transfer means for primary transfer the toner image formed on the surface of the image holder to the surface of the intermediate transfer body, and an intermediate transfer body. A configuration having a secondary transfer means for secondary transfer of the toner image transferred to the surface of the recording medium to the surface of the recording medium is applied. In that case, the primary transfer means includes the first transfer means and the second transfer means.

In the image forming apparatus according to the present embodiment, for example, a portion of each unit including each developing means may have a cartridge structure (process cartridge) to be attached to and detached from the image forming apparatus.

Hereinafter, in the image forming apparatus according to the present embodiment, the toner image formed on the surface of the image holder is primaryly transferred to the surface of the intermediate transfer body, and the toner image transferred to the surface of the intermediate transfer body is transferred to the surface of the recording medium. An intermediate transfer device for secondary transfer is shown as an example, but the present invention is not limited to this. The main parts shown in the figure will be described, and the description thereof will be omitted for the others.

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to the present embodiment.
As an example of the image forming apparatus according to the present embodiment, it is a tandem type configuration in which a plurality of image forming units are provided, a bright toner is used as a spot color toner, and an intermediate transfer belt is used as an intermediate transfer body to be transferred. An intermediate transfer type image forming apparatus equipped with the above will be described.

The image forming apparatus shown in FIG. 1 includes, for example, four image forming units 50Y, 50M, 50C, 50K for forming toner images of yellow, magenta, cyan, and black, respectively, and a developer containing a brilliant toner. Image forming units 50B that are used to form a brilliant toner image are arranged in parallel (in tandem) at intervals.
The image forming units are arranged in the order of the image forming units 50Y, 50M, 50C, 50K, and 50B from the upstream side in the rotation direction of the intermediate transfer belt 33.
Here, since each image forming unit 50Y, 50M, 50C, 50K, 50B has the same configuration except for the color of the toner in the stored developer, here, the image forming that forms a yellow image is formed. The unit 50Y will be described as a representative. In addition, by attaching a reference code with magenta (M), cyan (C), black (K), and silver (B) instead of yellow (Y) to the same portion as the image forming unit 50Y, each The description of the image forming units 50M, 50C, 50K, and 50B will be omitted.

Here, in the image forming apparatus shown in FIG. 1, the image forming units 50Y, 50M, and 50C all correspond to the first unit. Then, the developing devices 20Y, 20M, and 20C (that is, an example of the first developing means) of the image forming units 50Y, 50M, and 50C are provided with yellow toner, magenta toner, and cyan toner, respectively. And a first developer containing the carrier.
Further, the image forming unit 50K corresponds to a unit other than the first and second units. A developer (developer other than the first and second developer) containing a black toner and a carrier is housed in the developer 20K (an example of the developing means) of the unit 50K.
Further, the image forming unit 50B on the most downstream side corresponds to the second unit. Then, the developing apparatus 20B of the unit 50B (that is, an example of the first developing means) contains a second developing agent including a brilliant toner corresponding to the second toner and a second carrier. Has been done.

Here, since each of the units 50Y, 50M, 50C, 50K, and 50B has the same configuration except for the color of the toner in the stored developer, the unit 50Y forming the yellow image is represented here. I will explain.
However, the photoconductors 21Y, 21M, and 21C as image holders included in the units 50Y, 50M, and 50C, respectively, are formed on the first image holder by the respective toners 50Y, 50M, and 50C. The primary transfer rolls 17Y, 17M, and 17C, which transfer the image to the first toner image and the first toner image to the intermediate transfer belt 33, correspond to the first transfer means.
Further, the photoconductor 21B as an image holder included in the unit 50B is the second image holder, the toner image formed by the unit 50B is the second toner image, and the second toner image is on the intermediate transfer belt 33. The primary transfer roll 17B to be transferred corresponds to the second transfer means.
Hereinafter, the same parts as the unit 50Y are designated by reference numerals with magenta (M), cyan (C), black (K), and silver (B) instead of yellow (Y). The description of the units 50M, 50C, 50K, and 50B will be omitted.

The yellow image forming unit 50Y includes a photoconductor 21Y as an image holder, and the photoconductor 21Y is rotationally driven along a direction of arrow A shown by a driving means (not shown) at a predetermined process speed. It has become so. As the photoconductor 21Y, for example, an organic photoconductor having sensitivity in the infrared region is used.

A charging roll (charging means) 28Y is provided on the upper portion of the photoconductor 21Y, and a predetermined voltage is applied to the charging roll 28Y by a power source (not shown), and the surface of the photoconductor 21Y is predetermined. It is charged to the potential.

Around the photoconductor 21Y, an exposure device (static charge image forming means) 19Y that exposes the surface of the photoconductor 21Y to form an electrostatic charge image is arranged on the downstream side of the photoconductor 21Y in the rotation direction of the charge roll 28Y. Has been done. Here, as the exposure apparatus 19Y, an LED array that can be miniaturized is used due to space limitations, but the present invention is not limited to this, and an electrostatic charge image forming means using another laser beam or the like is used. But of course there is no problem.

Further, around the photoconductor 21Y, a developing device (developing means) 20Y provided with a developer holder for holding a yellow-colored developer is arranged on the downstream side of the photoconductor 21Y in the rotation direction of the exposure device 19Y. The electrostatic charge image formed on the surface of the photoconductor 21Y is visualized with a yellow-colored toner to form a toner image on the surface of the photoconductor 21Y.

Below the photoconductor 21Y, an intermediate transfer belt (transferred body, primary transfer means) 33 for primary transfer of a toner image formed on the surface of the photoconductor 21Y is provided with five photoconductors 21Y, 21M, 21C, 21K, 21B. It is arranged so as to extend below. The intermediate transfer belt 33 is pressed against the surface of the photoconductor 21Y by the primary transfer roll 17Y. Further, the intermediate transfer belt 33 is stretched by three rolls of the drive roll 22, the support roll 23, and the bias roll 24, and is rotated in the arrow B direction at a movement speed equal to the process speed of the photoconductor 21Y. It has become. A yellow toner image is primaryly transferred to the surface of the intermediate transfer belt 33, and magenta, cyan, black, and silver (brilliant) toner images are sequentially primary transferred and laminated.

Further, around the photoconductor 21Y, toner remaining on the surface of the photoconductor 21Y or retransferred toner is placed downstream of the primary transfer roll 17Y in the rotation direction (arrow A direction) of the photoconductor 21Y. A cleaning device 15Y for cleaning is arranged. As the cleaning device 15Y, a blade cleaning type device is used. The cleaning blade in the cleaning device 15Y is attached to the surface of the photoconductor 21Y so as to be in pressure contact with the surface in the counter direction.

The material of the cleaning blade is not particularly limited, and various elastic bodies are used. Specific examples of the elastic body include an elastic body such as a polyurethane elastic body, a silicone rubber, and a chloroprene rubber.

A secondary transfer roll (secondary transfer means) 34 is pressed against the bias roll 24 on which the intermediate transfer belt 33 is stretched via the intermediate transfer belt 33. The toner image that is primarily transferred and laminated on the surface of the intermediate transfer belt 33 is placed on the surface of the recording paper (recording medium) P that is fed from a paper storage container (not shown) at the pressure contact portion between the bias roll 24 and the secondary transfer roll 34. , Electrostatically transferred. At this time, since the silver toner image is on the top (top layer) of the toner image transferred and laminated on the intermediate transfer belt 33, the silver toner image is displayed on the toner image transferred to the surface of the recording paper P. It becomes the bottom (bottom layer).

Here, the intermediate transfer belt 33 preferably contains a polyimide resin or a polyamide-imide resin because the strength of the belt itself is high and the durability can be satisfied. The surface resistivity of the intermediate transfer belt 33 is preferably in the range of 1 × 10 ⁹ Ω / □ or more and 1 × 10 ¹⁴ Ω / □ or less. In order to control the surface resistivity, the intermediate transfer belt 33 contains a conductive filler as needed. Examples of the conductive filler include metal or alloys such as carbon black, graphite, aluminum and copper alloys, and metal oxidation such as tin oxide, zinc oxide, potassium titanate, tin oxide-indium oxide or tin oxide-antimony oxide composite oxide. A substance or a conductive polymer such as polyaniline is used alone or in combination of two or more kinds. Among them, carbon black is preferable as the conductive filler in terms of cost. Further, if necessary, a processing aid such as a dispersant or a lubricant may be added.

Further, downstream of the secondary transfer roll 34 (path not shown), the toner image multiplex-transferred on the recording paper P is fixed on the surface of the recording paper P by heat and pressure to form a permanent image. A fuser (fixing means) 35 is arranged.

As the fuser 35, for example, a fixing belt having a belt shape using a fluororesin component or a low surface energy material typified by a silicone resin on the surface, and a fluororesin component or a silicone resin on the surface are typified. Examples thereof include a cylindrical fixing roll using a low surface energy material.

The image forming apparatus shown in FIG. 1 includes toner cartridges 40B, 40Y, 40M, 40C, and 40K. The toner cartridges 40B, 40Y, 40M, 40C, and 40K are cartridges that contain toner of each color and are attached to and detached from the image forming apparatus. , Connected by a toner supply pipe (not shown). Then, when the amount of toner stored in each toner cartridge is low, the toner cartridge is replaced.

Next, the operation of each unit 50Y, 50M, 50C, 50K, 50B forming an image of each color of yellow, magenta, cyan, black, and silver (brilliant) will be described. Since the operations of the units 50Y, 50M, 50C, 50K, and 50B are the same, the operation of the yellow unit 50Y will be described as a representative thereof.

In the yellow unit 50Y, the photoconductor 21Y rotates at a predetermined process speed in the direction of arrow A. The surface of the photoconductor 21Y is negatively charged to a predetermined potential by the charging roll 28Y. After that, the surface of the photoconductor 21Y is exposed by the exposure apparatus 19Y, and a static charge image corresponding to the image information is formed. Subsequently, the negatively charged toner is reverse-developed by the developing apparatus 20Y, and the electrostatic charge image formed on the surface of the photoconductor 21Y is visualized on the surface of the photoconductor 21Y to form a toner image. After that, the toner image on the surface of the photoconductor 21Y is primarily transferred to the surface of the intermediate transfer belt 33 by the primary transfer roll 17Y. After the primary transfer, the transfer residual component such as toner remaining on the surface of the photoconductor 21Y is scraped off by the cleaning blade of the cleaning device 15Y and cleaned to prepare for the next image forming step.

The above operation is performed on each unit 50Y, 50M, 50C, 50K, 50B, and toner images visualized on the surfaces of the photoconductors 21Y, 21M, 21C, 21K, and 21B are formed one after another on the intermediate transfer belt 33. Multiple transfer is performed on the surface. In color mode, toner images of each color are transferred in the order of yellow, magenta, cyan, black, and silver (brilliance), but even in two-color and three-color mode, the required colors are transferred in this order. Only the toner image will be transferred individually or multiple times. After that, the toner image transferred alone or multiple times on the surface of the intermediate transfer belt 33 is secondarily transferred to the surface of the recording paper P conveyed from the paper cassette (not shown) by the secondary transfer roll 34, and subsequently, the fixing device 35. It is fixed by heating and pressurizing in. The toner remaining on the surface of the intermediate transfer belt 33 after the secondary transfer is cleaned by the belt cleaner 26 composed of the cleaning blade for the intermediate transfer belt 33.
Further, the intermediate transfer belt 33 on which the toner image is transferred alone or multiple times is statically eliminated by the drive roll 22.

The image forming apparatus shown in FIG. 1 uses a charging roll as the charging device, but is not limited to this, for example, a contact-type charger using a charging brush, a charging film, a charging rubber blade, a charging tube, or the like, and non-contact. A roll charger of the type, a scorotron charger using corona discharge, a charger known per se, such as a corotron charger, and the like are also used.

In the image forming apparatus shown in FIG. 1, a primary transfer roll is used as the primary transfer means and a secondary transfer roll is used as the secondary transfer means, but the present invention is not limited to this, and for example, a belt, a film, a rubber blade, or the like is used. A transfer charger known per se, such as a contact type transfer charger, a scorotron transfer charger using corona discharge, or a corotron transfer charger, may be used.

In the image forming apparatus shown in FIG. 1, five units 50Y, 50M, 50C, 50K, and 50B are arranged in this order from the upstream side in the rotation direction of the intermediate transfer belt 33, and the units 50Y, 50M, and the unit 50M are arranged in this order. 50C is the first unit and unit 50B is the second unit.
The image forming apparatus according to the present embodiment is not limited to the above embodiment, and the arrangement order is not limited to this as long as the second unit is arranged on the downstream side of the first unit.
Further, in the image forming apparatus shown in FIG. 1, the unit 50B, which is the second unit, is provided on the most downstream side in the rotation direction of the intermediate transfer belt 33 among all the units, but the present invention is not limited to this. Further units may be provided on the downstream side of the second unit.
In the image forming apparatus shown in FIG. 1, three units 50Y, 50M, and 50C, which are the first units, are provided on the upstream side of the second unit, but one or two of them are other units. It may be a unit of.
Since the first carrier housed in the first unit is likely to be mixed with the second developing means in the adjacent second unit, the first unit is similar to the image forming apparatus shown in FIG. And the second unit are preferably adjacent to each other. Further, from the viewpoint of effectively suppressing the occurrence of white spots, it is preferable that all the units on the upstream side of the second unit are the first units.

In the image forming apparatus shown in FIG. 1, five units are arranged along the rotation direction of the intermediate transfer belt 33, but the number of units may be two or more. The number of units is preferably 3 or more and 5 or less.
In the image forming apparatus shown in FIG. 1, as the first unit, an image forming unit that forms a transparent toner image by using a developing agent containing a transparent toner may be provided. Further, as the second unit, a white toner image is formed by using a developer containing a white toner in place of an image forming unit that forms a toner image having a brilliant property by using a developer containing a brilliant toner. It may have an image forming unit to be processed.

The unit 50B in the image forming apparatus shown in FIG. 1 includes a developing device 20B including a developer holder for holding a silver (brilliant) color developer, a photoconductor 21B, a charging roll 28B, and a cleaning device 15B. It may be configured as a process cartridge that is attached to and detached from the image forming apparatus main body. Further, the units 50M, 50C, 50K, and 50B may also be configured as process cartridges in the same manner as the unit 50Y.
The configuration of the process cartridge will be described below.

FIG. 2 shows an example of a process cartridge. However, the process cartridge is not limited to the form shown in FIG. The main parts shown in the figure will be described, and the description thereof will be omitted for the others.
The process cartridge 200 shown in FIG. 2 is provided around the photoconductor 207 (an example of an image holder) and the periphery of the photoconductor 207 by, for example, a housing 217 provided with a mounting rail 216 and an opening 218 for exposure. The charged roll 208 (an example of the charging means), the developing device 211 (an example of the developing means), and the photoconductor cleaning device 213 (an example of the cleaning means) are integrally combined and held and configured to form a cartridge. There is.
In FIG. 2, 209 indicates an exposure apparatus (an example of an electrostatic charge image forming means), 212 indicates a primary transfer roll (an example of a primary transfer means), and 220 indicates an intermediate transfer belt (an example of an intermediate transfer body).
The process cartridge is not limited to the above configuration, and is at least selected from a developing device and, if necessary, other means such as an image holder, a charging means, an electrostatic charge image forming means, and a transfer means. It may be configured to include one.

Hereinafter, the present embodiment will be described in detail with reference to Examples, but the present embodiment is not limited to these Examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

[Creation of carrier]
(Making carrier 1-1)
-Mn-Mg ferrite particles (volume average particle size 37 μm): 100 parts-Cyclohexyl methacrylate: 3 parts-Melamine resin particles: ("Eposter S (manufactured by Nippon Shokubai)",
Melamine / formaldehyde condensed resin particles, average particle size 350 nm) 0.30 part / toluene 14 parts Of the components shown in the above carrier composition, each component excluding Mn-Mg ferrite particles and glass beads (φ1 mm, same amount as toluene) Was stirred at 1200 rpm for 30 minutes using a sand mill manufactured by Kansai Paint Co., Ltd. to obtain a resin coating layer forming solution 1. Further, the resin coating layer forming solution 1 and the Mn—Mg ferrite particles were placed in a vacuum degassing type kneader, and toluene was distilled off to form a resin-coated carrier. Subsequently, the carrier 1-1 was obtained by removing fine powder and coarse powder with an elbow jet.

(Making carrier 1-2)
Carrier 1-2 was obtained in the same manner as carrier 1-1 except that the number of copies of the melamine resin particles was changed to 0.25.

(Making carriers 1-3)
Carriers 1-3 were obtained in the same manner as in Carrier 1-1, except that the number of copies of the melamine resin particles was changed to 0.32.

(Preparation of carriers 1-4)
Carriers 1-4 were obtained in the same manner as carriers 1-1 except that the number of copies of the melamine resin particles was changed to 0.36.

(Preparation of carrier 1-5)
Carriers 1-5 were obtained in the same manner as in Carrier 1-1 except that the number of copies of the melamine resin particles was changed to 0.40.

(Preparation of carrier 1-6)
Carriers 1-6 were obtained in the same manner as in Carrier 1-1 except that the number of parts of the melamine resin particles was changed to 0.44.

(Preparation of carrier 1-7)
Carrier 1-similar to Carrier 1-1, except that the melamine resin particles were changed to benzoquinamine resin particles (“Epostal MS (manufactured by Nippon Catalyst)”, benzoquanamine / formaldehyde condensed resin particle classification product, average particle size 800 nm). I got 7.

(Preparation of carrier 1-8)
Carrier 1-1 except that the melamine resin particles were changed to "Epostal SS (manufactured by Nippon Catalyst)" (melamine / formaldehyde condensed resin particles, average particle size 120 nm) and the number of melamine resin particles was changed to 0.40. Carriers 1-8 were obtained in the same manner.

(Preparation of carrier 1-9)
Carriers 1-9 were obtained in the same manner as in Carrier 1-1 except that the number of copies of the melamine resin particles was changed to 0.50.

[Making toner]
(Manufacturing of toner 2B (brilliant toner))
<Making polyester resin>
-Dimethyl adipate: 74 parts-Dimethyl terephthalate: 192 parts-Bisphenol A ethylene oxide adduct: 216 parts-Ethylene glycol: 38 parts-Tetrabutoxytitanate (catalyst): 0.037 parts Put it in a flask, introduce nitrogen gas into the container, keep it in an inert atmosphere and raise the temperature while stirring, then carry out a polycondensation reaction at 160 ° C for 7 hours, and then gradually reduce the pressure to 10 Torr and raise it to 220 ° C. It was warmed and held for 4 hours. Then, the pressure was returned to normal pressure, 9 parts of trimellitic anhydride was added, the pressure was gradually reduced to 10 Torr again, and the mixture was kept at 220 ° C. for 1 hour to obtain a polyester resin. The glass transition temperature (Tg) of the polyester resin was 64 ° C.

<Preparation of resin particle dispersion>
-Polyester resin: 160 parts-Ethyl acetate: 233 parts-Sodium hydroxide aqueous solution (0.3N): 0.1 parts Put the above material in a 1 L separable flask and heat it at 70 ° C. ) To prepare a resin mixture. While further stirring this resin mixture at 90 rpm, 373 parts of ion-exchanged water was gradually added for phase inversion emulsification and solvent removal to obtain a resin particle dispersion (solid content concentration 30%).

<Preparation of bright pigment dispersion liquid>
・ Flat aluminum pigment (2173EA of Toyo Aluminum): 100 parts ・ Anionic surfactant (Neogen R of Dai-ichi Kogyo Seiyaku Co., Ltd.): 1.5 parts ・ Ion-exchanged water: 900 parts Emulsification disperser by mixing the above materials The dispersion treatment with (Cavitron CR1010 of Pacific Kiko) was carried out for 1 hour to obtain a bright pigment dispersion liquid (solid content concentration 10%).

<Preparation of mold release agent dispersion>
・ Carnauba wax (RC-160 of Toa Kasei Kogyo): 50 parts ・ Anionic surfactant (Neogen RK of Daiichi Kogyo Seiyaku Co., Ltd.): 1.0 part ・ Ion exchange water: 200 parts Mix the above materials at 95 ° C. Then, a homogenizer (Ultratarax T50 manufactured by IKA) was used for dispersion treatment, and then a manton Goulin high-pressure homogenizer (Gorin Co., Ltd.) was used for dispersion treatment for 360 minutes. Got The volume average particle size of the release agent particles in the release agent dispersion was 230 nm.

<Preparation of brilliant toner particles>
-Resin particle dispersion: 500 parts (solid content concentration 30%)
-Glittering pigment dispersion: 350 parts (solid content concentration 10%)
-Release release agent dispersion: 50 parts (solid content concentration 20%)
Nonionic surfactant (Igepal CA897): 1.40 parts Put the above raw materials in a 2 L cylindrical stainless steel container (diameter 30 cm) and disperse while applying shear force at 4000 rpm with a homogenizer (Ultratalax T50 from IKA). The treatment was carried out for 10 minutes. Next, 1.75 parts of a 10% aqueous solution of polyaluminum chloride was gradually added dropwise, the homogenizer rotation speed was set to 5000 rpm, and the dispersion treatment was performed for 15 minutes to prepare a raw material dispersion liquid.

Next, the raw material dispersion was transferred to a polymerization kettle equipped with a stirrer having a stirring blade with two paddles and a thermometer, and heating was started with a mantle heater while stirring at a stirring rotation speed of 200 rpm, and held at 54 ° C. for 2 hours. To form the first aggregate. At this time, the pH of the raw material dispersion was controlled to 2.2 to 3.5 with 0.3N nitric acid and 1N sodium hydroxide aqueous solution.
Next, 123 parts of the resin particle dispersion liquid was additionally added, and the resin particles were adhered to the surface of the first aggregate to form the second aggregate. Then, the temperature was raised to 56 ° C., and the mixture was held for 2 hours while confirming the morphology and size of the second aggregate with an optical microscope and Multisizer II (Beckman Coulter). Then, after raising the pH to 8.0, the temperature was raised to 67.5 ° C. to fuse the second aggregate, the pH was lowered to 6.0 while maintaining the temperature at 67.5 ° C., and the heating was stopped after 1 hour. , 0.1 ° C./min cooling rate. Then, the particles were sieved with a 20 μm mesh, washed with water repeatedly, and then dried with a vacuum dryer to obtain brilliant toner particles. The volume average particle size of the brilliant toner particles was 9 μm.

<Making external toner>
100 parts of the obtained brilliant toner particles and 1.5 parts of hydrophobic silica (RY50 of Nippon Aerosil) were mixed with a Henschel mixer at a peripheral speed of 33 m / s for 2 minutes. Then, the mixture was sieved with a vibrating sieve having an opening of 45 μm to obtain toner 2B, which is an externally added brilliant toner.

(Making toner 1K (black toner))
<Colorant particle dispersion K>
-Carbon black: 50 parts-Anionic surfactant: 5 parts-Ion-exchanged water: 200 parts Mix the above components and disperse them with IKA Ultratarax for 5 minutes and then with an ultrasonic bath for 10 minutes to obtain solid content. A 21% black colorant particle dispersion K was obtained.

<Release Release Agent Particle Dispersion 1>
・ Paraffin wax: HNP-9 (manufactured by Nippon Seiro Co., Ltd.): 19 parts ・ Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1 part ・ Ion exchanged water: 80 parts The mixture was mixed at 90 ° C., heated to 90 ° C., and stirred for 30 minutes. Next, the melt was circulated from the bottom of the container to the Gorin homogenizer, and a circulation operation equivalent to 3 passes was performed under a pressure condition of 5 MPa. After that, the pressure was increased to 35 MPa, and a circulation operation equivalent to 3 passes was further performed. The emulsion thus formed was cooled in the heat-resistant solution until the temperature became 40 ° C. or lower to obtain a release agent particle dispersion liquid 1.

<Resin particle dispersion liquid 1>
-Oil phase-
・ Styrene (manufactured by Wako Pure Chemical Industries, Ltd.): 30 parts ・ n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.): 10 parts ・ β-carboxyethyl acrylate (manufactured by Solvay Nikka Co., Ltd.): 1.3 parts ・ Dodecane Styrene (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 copies

-Aquatic phase 1-
・ Ion-exchanged water: 17 parts ・ Anionic surfactant (Dowfax, manufactured by Dow Chemical Co., Ltd.): 0.4 parts

-Aquatic phase 2-
-Ion-exchanged water: 40 parts-Anionic surfactant (Dowfax, manufactured by Dow Chemical Industries, Ltd.): 0.05 parts-Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries, Ltd.): 0.4 parts

The components of the oil phase and the components of the aqueous phase 1 were placed in a flask and mixed by stirring to obtain a monomeric emulsified dispersion.
The components of the aqueous phase 2 were put into the reaction vessel, the inside of the vessel was sufficiently replaced with nitrogen, and the inside of the reaction system was heated to 75 ° C. with an oil bath while stirring.
Further, the above-mentioned monomer emulsified dispersion was gradually added dropwise into the reaction vessel over 3 hours to carry out emulsion polymerization. After the dropping was completed, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours.

The obtained resin particles were found to be 250 nm when the volume average particle size D50v of the resin particles was measured with a laser diffraction type particle size distribution measuring device LA-700 manufactured by HORIBA, Ltd.).
The glass transition temperature of the resin was measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC-50 manufactured by Shimadzu Corporation) and found to be 52 ° C.
The number average molecular weight (in terms of polystyrene) was measured using a molecular weight measuring device (HLC-8020 manufactured by Tosoh Corporation) using THF (tetrahydrofuran) as a solvent and found to be 13,000.
As a result, a resin particle 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 particles K>
・ Resin particle dispersion 1: 50 parts ・ Colorant particle dispersion K: 30 parts ・ Release agent particle dispersion 1: 40 parts ・ Polyaluminum chloride: 0.4 parts

After each of the above components was sufficiently mixed and dispersed in a stainless steel flask using Ultratalax manufactured by IKE, the flask was heated to 48 ° C. while stirring in a heating oil bath. After holding at 48 ° C. for 80 minutes, 70 parts of the same resin particle dispersion 1 as above was slowly 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 flask was sealed, the stirring shaft was magnetically sealed, and stirring was continued. It was heated to 97 ° C. and held for 3 hours. After completion of the reaction, the temperature was lowered to 1 ° C./min, and the mixture was filtered and washed with ion-exchanged water, and then solid-liquid separation was performed by Nucci-type suction filtration. This was further redispersed using 3 L of ion-exchanged water at 40 ° C., and the mixture was stirred and washed at 300 rpm for 15 minutes.
This washing operation was repeated 5 more times, and when the pH of the filtrate became 6.54 and the electrical conductivity was 6.5 μS / cm, solid-liquid separation was performed using filter paper (No. 5A) by Nucci type suction filtration. rice field. Then, vacuum drying was continued for 12 hours to obtain toner particles K.

The volume average particle size of the toner particles K was measured using a Coulter Multisizer-Type II (Beckman-Coulter) with an aperture diameter of 50 μm and found to be 6.2 μm, with a volume particle size distribution index GSDv of 1.20. there were.
When the shape was observed with a Luzex image analyzer manufactured by Luzex, it was observed that the shape coefficient SF1 of the particles was 135.
The glass transition temperature of the toner particles K was 52 ° C.

<External addition of external preparation>
Further, the toner particles K are treated with hexamethyldisilazane (HMDS) to surface-hydrophobicize the primary particles of silica (SiO ₂ ) particles having an average particle size of 40 nm, and the primary product of metatitanic acid and isobutyltrimethoxysilane. Metatitanic acid compound particles having an average particle size of 20 nm were added so that the coverage of the toner particles K on the surface was 40%, and the mixture was mixed with a Henshell mixer to prepare toner 1K as a black toner.

(Manufacturing of toner 1Y (yellow toner), toner 1M (magenta toner), and toner 1C (cyan toner))
<Colorant particle dispersions Y, M, and C>
In the preparation of the colorant particle dispersion K, instead of carbon black, a yellow pigment (PY180: manufactured by Clariant Japan), a magenta pigment (PR122: manufactured by Dainichi Ink Chemical Co., Ltd.), and a cyan pigment (copper phthalocyanine, CI. Pigment blue 15: 3: manufactured by Dainichi Seika Co., Ltd.), the same as the colorant particle dispersion K for black, the colorant particle dispersion Y for yellow, and the colorant particle dispersion M for magenta. , And a colorant particle dispersion C for cyanide were obtained.

<Preparation of toner particles Y, M, and C>
In the production of the toner particles K, the colorant particle dispersion K for black is used as the colorant particle dispersion Y for yellow, the colorant particle dispersion M for magenta, and the colorant particle dispersion C for cyan, respectively. Toner particles Y for yellow, toner particles M for magenta, and toner particles C for cyan were produced in the same manner as the toner particles K for black except that the toner particles K were changed to.

<External addition of external preparation>
Similar to toner 1K, which is a toner for black, except that toner particles Y, toner particles M, and toner particles C are used instead of toner particles K, for toner 1Y and magenta, which are toners for yellow. Toner 1M, which is the toner of the above, and toner 1C, which is the toner for cyanide, were obtained.

(Making toner 2W (white toner))
<Colorant particle dispersion W>
-Titanium oxide particles (1) (manufactured by Ishihara Sangyo Co., Ltd., product name: CR-60-2): 210 parts-Nonionic surfactant (manufactured by Sanyo Chemical Industries, Ltd., product name: Nonipole 400): 10 parts-Ion-exchanged water : 480 parts The above materials are mixed, stirred for 30 minutes using a homogenizer (Ultratalax T50 manufactured by IKA), and then 1 hour with a high pressure impact disperser Ultimizer (HJP30006: manufactured by Sugino Machine Limited). Distributed processing was performed. Further, the supernatant was removed by allowing to stand to prepare a colorant particle dispersion W (solid content concentration: 30%) in which titanium oxide particles having a number average particle size of 300 nm were dispersed.

<Preparation of toner particles W>
In the production of the toner particles K, the toner particles W for white were used in the same manner as the toner particles K for black, except that the colorant particle dispersion K for black was changed to the colorant particle dispersion W for white. Made.

<External addition of external preparation>
Toner 2W, which is a toner for white, was obtained in the same manner as toner 1K, which is a toner for black, except that toner particles W were used instead of the toner particles K.

[Preparation of developer]
100 parts of the carrier shown in Table 3 and 10 parts of the toner shown in Table 3 were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sheave having a mesh of 125 μm to obtain each developer.

<Examples 1 to 10, Comparative Examples 1 and 2>
Using the image forming apparatus shown in FIG. 1 (manufactured by Fuji Xerox Co., Ltd., model number: DocuCenterColor400 modified machine: intermediate transfer method), the developing apparatus 20Y, 20M, 20C, 20K of the units 50Y, 50M, 50C, 50K, and 50B. , And 20B were filled with the developing agents shown in Table 4, respectively.

Using this device, a yellow toner image with a toner loading amount of 3.8 g / m ² and a magenta toner image with a toner loading amount of 3.8 g / m ² and a toner loading amount of 3.8 g / m ² are used on the intermediate transfer belt. A solid batch toner image (5.2 cm x 1.2 cm image) transferred by superimposing a cyan toner image and a brilliant toner image with a toner loading amount of 4.4 g / m ² on A4 size plain paper (C2 paper, Fuji). After transferring to Xerox Co., Ltd.), it became established.

1000 sheets of the above image formation were output on plain paper under a high temperature and high humidity (temperature 30 ° C. and humidity 85% RH) environment and a low temperature and low humidity (temperature 10 ° C. and humidity 10% RH) environment.
Then, the following evaluation was performed on the solid batch images output on the first (initial) and 1000th images.

CIE1976L ^* a ^* b ^* Coordinate values (L ^* ) of the color system using X-Rite 939 (aperture diameter 4 mm) manufactured by X-Rite Co., Ltd. for each of the peripheral part (10 mm from the edge) of the image and 10 places inside the image. The value, a ^* value and b ^* value) were obtained.
Then, the color difference (maximum color difference ΔE) from the measurement point where the color difference ΔE is maximum was obtained with respect to the average value of the L ^* value, the a ^* value, and the b ^* value. Then, it was evaluated according to the following evaluation criteria.
The color difference ΔE is defined by ΔE = ((Δa) ² + (Δb) ² + (ΔL) ² ) ^1/2 . The smaller the maximum color difference ΔE, the smaller the density unevenness.

-Evaluation criteria-
A: The density variation on the image is ΔE <0.3, which cannot be visually determined, and there is no problem with the image quality.
B: The density variation ΔE on the image is 0.3 to 0.5, and there is slight unevenness, but there is no problem in image quality.
C: The density variation ΔE on the image is 0.5 to 1.0, and slight unevenness is observed.
D: Density variation on the image ΔE> 1.0, and clear density unevenness is observed on the image.

Further, for the image using the developer W containing white toner, the image hiding property was evaluated according to the following criteria.
A: The colored image is completely concealed on the paper, and the density variation ΔE from the limit sample is within 0 to 0.5, and there is no problem in image quality.
B: The colored image is not completely concealed on the paper, and a clear density unevenness is observed on the image with a density variation ΔE> 1.0 from the limit sample.

The details of each example are listed below in Tables 1 to 4.
The details of the abbreviations in the table are as follows.
-N particles: nitrogen-containing particles-N1: Content of nitrogen-containing particles on the surface of the first carrier (N1)
N2: Content of nitrogen-containing particles on the surface of the second carrier (N2)

From the above results, it can be seen that the occurrence of density unevenness is suppressed in this example as compared with the comparative example.

15B, 15Y, 15M, 15C, 15K Cleaning device 17B, 17Y, 17M, 17C, 17K, 212 Primary transfer roll 19B, 19Y, 19M, 19C, 19K, 209 Exposure device 20B, 20Y, 20M, 20C, 20K, 211 Development Equipment 21B, 21Y, 21M, 21C, 21K, 207 Photoreceptor 22 Drive roll 23 Support roll 24 Bias roll 26 Belt cleaner 28B, 28Y, 28M, 28C, 28K, 208 Charging roll 33, 220 Intermediate transfer belt 34 Secondary transfer roll 35 Fuser 40B, 40Y, 40M, 40C, 40K Toner cartridge 50B, 50Y, 50M, 50C, 50K Image forming unit 200 Process cartridge 213 Photoreceptor cleaning device 216 Mounting rail 217 Housing 218 Opening P Recording paper

Claims (13)

It has a first developer containing a first toner other than the black toner and a first carrier, and a second developer containing a second toner and a second carrier.
The first carrier and the second carrier include a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles.
The dielectric loss rate of the second toner is higher than that of the first toner.
A developer set in which the content (N1) of the nitrogen-containing particles on the surface of the first carrier is higher than the content (N2) of the nitrogen-containing particles on the surface of the second carrier. It has a first developer containing a first toner other than the black toner and a first carrier, and a second developer containing a second toner and a second carrier.
The first carrier and the second carrier include a magnetic core material and a coating resin layer that covers the magnetic core material and contains nitrogen-containing particles.
At least one of the specific gravity and the volume average particle diameter of the second toner is higher than that of the first toner.
A developer set in which the content (N1) of the nitrogen-containing particles on the surface of the first carrier is higher than the content (N2) of the nitrogen-containing particles on the surface of the second carrier. The ratio of the content of the nitrogen-containing particles (N1) on the surface of the first carrier to the content (N2) of the nitrogen-containing particles on the surface of the second carrier is
1.10 <N1 / N2 <2.50
The developer set according to claim 1 or claim 2. The ratio is
1.6 <N1 / N2 <2.2
The developer set according to claim 3. The content (N1) of the nitrogen-containing particles on the surface of the first carrier is
6.0 <N1 <8.0
The developer set according to any one of claims 1 to 4, which satisfies the above conditions. The content (N1) of the nitrogen-containing particles on the surface of the first carrier is
7.0 <N1 <7.8
The developer set according to claim 5. The developer set according to any one of claims 1 to 6, wherein the nitrogen-containing particles have an average particle diameter of 100 nm or more and 800 nm or less. The developer set according to claim 7, wherein the nitrogen-containing particles have an average particle diameter of 300 nm or more and 500 nm or less. The developer set according to any one of claims 1 to 8, wherein the nitrogen-containing particles include at least one selected from the group consisting of melamine resin particles and benzoquanamine resin particles. The developer set according to claim 9, wherein the nitrogen-containing particles are melamine resin particles. The first developer is
A yellow developer containing yellow toner as the first toner,
A magenta developer containing magenta toner as the first toner,
One of claims 1 to 10, which comprises at least one selected from the group consisting of a cyan developer containing cyan toner as the first toner and a clear developer containing clear toner as the first toner. The developer set according to item 1. The second developer is
The one according to any one of claims 1 to 11, wherein the second toner contains at least one of a white developer containing a white toner and the second toner contains a brilliant developer containing a brilliant toner. Developer set. Among the developer sets according to any one of claims 1 to 12, the first image forming unit containing the first developer and the first image forming unit.
The developer set according to any one of claims 1 to 12, comprising a second image forming unit containing the second developer.
The first image forming unit and the second image forming unit are arranged along the traveling direction of the transferred body.
An image forming apparatus in which the second image forming unit is arranged downstream of the first image forming unit in the traveling direction of the transferred body.

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