JP2011064907A - Image forming apparatus and toner set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that reduces image defects when fixed images are stacked and stored as compared with a case where the melting temperature of a mold release agent contained in black toner is not lower than that of a mold release agent contained in toner of the other color by 3°C or more. <P>SOLUTION: The image forming apparatus includes a first image forming unit for forming a black toner image with black toner, and a second image forming unit for forming a toner image of the other color with toner other than the black toner. Each of the black toner and the toner other than the black toner contains at least a colorant, binder resin, and mold release agent. The melting temperature of the mold release agent contained in the black toner is lower than that contained in the toner other than the black toner by 3°C or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Attempts have been made to improve the image quality of toner images in image forming apparatuses that form toner images. For example, a method of increasing the fixing tolerance by increasing the amount of the release agent added to the black toner as compared with the color toner is disclosed (for example, Patent Document 1). Further, a method is disclosed in which the softening temperature of the black toner is made higher than the softening temperature of the color toner and the amount of polyolefin wax added to the black toner is less than that of the color toner (for example, see Patent Document 2).

JP 2005-99400 A JP 2001-147555 A

  An object of the present invention is to fix a fixed image compared to the case where the melting temperature of the release agent contained in the black toner is not lower by 3 ° C. or more than the melting temperature of the release agent contained in the toner of a color other than black. The object is to suppress the occurrence of image loss when the images are stored repeatedly.

Specific means for achieving the above object are as follows.
The invention according to claim 1
A first image forming unit that forms a black toner image with black toner;
A second image forming unit that forms a toner image of a different color with toner of a color other than black;
Have
Each of the black toner and the non-black toner contains at least a colorant, a binder resin, and a release agent, and the melting temperature of the release agent contained in the black toner is contained in a toner other than black. The image forming apparatus is lower by 3 ° C. or more than the melting temperature of the release agent.

The invention according to claim 2
The image forming apparatus according to claim 1, wherein a melting temperature of the release agent for the black toner is 75 ° C. or higher, and a melting temperature of the release agent contained in the toner of a color other than black is 80 ° C. or higher. It is.

The invention according to claim 3
The image forming apparatus according to claim 1, wherein an exposure rate of the release agent on the surface of the black toner is 0 atm% or more and 20 atm% or less.

The invention according to claim 4
A black toner containing at least a black colorant, a binder resin and a release agent;
A toner of a color other than black containing at least a colorant other than black, a binder resin and a release agent,
In this toner set, the melting temperature of the release agent contained in the black toner is lower by 3 ° C. or more than the melting temperature of the release agent contained in the toner of a color other than black.

  According to the first aspect of the present invention, the melting temperature of the release agent contained in the black toner is not 3 ° C. lower than the melting temperature of the release agent contained in the toner of a color other than black. There is provided an image forming apparatus capable of suppressing the occurrence of image loss when a fixed image is stored in an overlapping manner.

  According to the second aspect of the invention, the melting temperature of the release agent for the black toner is not 75 ° C. or higher, and the melting temperature of the release agent contained in the toner of a color other than black is not 80 ° C. or higher. The occurrence of image loss when the fixed images are stored in an overlapping manner can be suppressed.

  According to the invention of claim 3, the image quality is excellent as compared with the case where the exposure rate of the release agent on the surface of the black toner is not 0% or more and 20% or less.

  According to the invention of claim 4, the melting temperature of the release agent contained in the black toner is not lower than the melting temperature of the release agent contained in the toner of a color other than black by 3 ° C. or more. In addition, a toner set is provided in which occurrence of image loss when a fixed image is stored in an overlapping manner is suppressed.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

  The image forming apparatus according to the present embodiment includes at least a first image forming unit that forms a black toner image with black toner, a second image forming unit that forms another color toner image with toner of a color other than black, Is provided. Further, the black toner and the non-black toner each contain at least a colorant, a binder resin, and a release agent, and the melting temperature of the release agent contained in the black toner is a toner of a color other than black. 3 ° C. or lower than the melting temperature of the release agent contained in.

<Toner>
First, the toner applied to the image forming apparatus of this embodiment will be described in detail.
The toner according to the exemplary embodiment includes at least a release agent, a binder resin, and a colorant. If necessary, silica or a charge control agent may be used. Further, an external additive may be added.

-Release agent-
In the image forming apparatus of the present embodiment, an image is formed by using black toner and a toner of a color other than black (hereinafter sometimes referred to as “other color toner”). The melting temperature of the release agent contained in the black toner is 3 ° C. or more lower than the melting temperature of the release agent contained in the other color toner.

  Here, “the melting temperature of the release agent contained in the black toner is 3 ° C. or more lower than the melting temperature of the release agent contained in the other color toner” means that the other color toner is from a plurality of color toners. When configured, the melting temperature of the release agent contained in the black toner is 3 ° C. or higher compared to the release agent having the lowest melting temperature among the release agents contained in the plurality of other color toners. Means low.

  As a result of studies by the present inventors, it has been clarified that the occurrence of image loss when a fixed image is stored in a superimposed manner is more conspicuous when a character image is superimposed than a solid image (solid image). In a character image, the internal cohesive force is small, so it is presumed that the image is likely to be lost.

  Therefore, in the present embodiment, image loss is suppressed by exposing more release agent on the surface of black toner that is often used for forming character images. When the resins containing the colorant are in direct contact with each other, the colorant moves together with the resin from one image in contact with the other to cause an image defect. However, since the release agent does not contain a colorant, if the release agent is exposed on the image surface, the release agents come into contact with each other, and the release agent may migrate during storage, but the colorant. Does not migrate and image loss is suppressed.

In general, an image of a color other than black is formed by superimposing a plurality of color toners, whereas a black image is formed only of black toner, so that the height (thickness) of the toner image is increased. It is low in the black image area, and it is difficult to apply pressure during fixing. As a result, the release agent in the black toner is hardly exposed on the surface.
In the case of a character image, unlike a solid image, a concave portion is hardly formed on the surface of the image, so that the release agent exposed on the surface is difficult to accumulate. Also from this point, the amount of the release agent remaining on the surface of the fixed image is smaller in the character image than in the solid image.

  From the above, in the character image formed with the black toner, it is presumed that the coating amount of the release agent on the surface tends to be smaller than the image of other colors, and the image is easily lost. . However, in the present embodiment, a larger amount of the release agent is exposed on the surface of the black toner used for forming the character image, so that image loss can be suppressed.

  As a specific measure for exposing more release agent on the surface of the character image, a release agent having a melting temperature lower than that of the other color toner is used for the black toner. In particular, if the melting temperature of the release agent in the black toner is lower by 3 ° C. or more than the melting temperature of the release agent in the other color toner, the amount of the release agent exposed on the image surface may cause image defects during storage. It becomes effective to suppress.

  Furthermore, the melting temperature of the release agent in the black toner is preferably 3 ° C. or more and 15 ° C. or less lower than the melting temperature of the release agent in the other color toner, more preferably 4 ° C. or more and 10 ° C. or less. Is preferred.

  The melting temperature of the release agent contained in the black toner is preferably 75 ° C. or higher and preferably 75 ° C. or higher and 100 ° C. or lower in view of the image quality and taking into consideration the appropriate exposure amount on the image surface. More desirably, it is 77 ° C. or more and 95 ° C. or less.

  The melting temperature of the release agent contained in the other color toner is preferably 80 ° C. or higher, more preferably 80 ° C. or higher and 105 ° C. or lower, and 85 ° C. or higher and 100 ° C. or lower from the viewpoint of image quality. More desirable is.

  The melting temperature of the release agent in the toner is measured by thermal analysis. Specifically, the main maximum endothermic peak measured using DSC-60 (manufactured by Shimadzu Corporation) according to ASTM D3418-8 is the melting temperature of the release agent in the toner.

  Further, in consideration of image quality while suppressing image loss during storage, the exposure rate at which the release agent is exposed on the surface of the black toner is preferably 0 atm% or more and 20 atm% or less, and 0 atm% or more and 15 atm% or less. It is more desirable that it is 0 atm% or more and 10 atm% or less.

  The said exposure rate is measured by isolate | separating and quantifying the peak resulting from resin, a pigment, and a mold release agent by X-ray photoelectron spectroscopy (XPS).

  The exposure rate can be adjusted by controlling the internal structure of the toner using a chemical manufacturing method. The method of adding a release agent during toner production and the compatibility between the release agent and the binder resin are adjusted. Examples thereof include a method, a method of forming a shell of resin, and concealing the release agent. A specific method will be described later.

  Examples of the toner particle releasing agent include low molecular weight polyolefin waxes such as polyethylene, polypropylene and polybutene; plant waxes such as carnauba wax, rice wax, candelilla wax, wood wax and jojoba oil; beeswax and the like Examples include animal waxes; mineral / petroleum waxes such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax; and modified products thereof.

  In particular, it is preferable to use Fischer-Tropsch wax, paraffin wax, microcrystalline wax, and polyolefin wax as the black toner release agent from the viewpoint of exposing the release agent to the toner surface.

  On the other hand, it is preferable to use Fischer-Tropsch wax, paraffin wax, microcrystalline wax, and polyolefin wax as the releasing agent for the other color toner.

  The addition amount of the release agent in the black toner is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 12% by mass or less, taking image quality deficiency or image quality into consideration. More preferably, the content is 3% by mass or more and 10% by mass or less.

  The addition amount of the release agent in the other color toner is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 12% by mass or less in consideration of image quality and the like. It is further desirable that the content is not less than 10% and not more than 10% by mass.

  The melt viscosity of the release agent is desirably 1 mPa · s or more and 10 mPa · s or less at 120 ° C. More desirably, it is 2 mPa · s or more and 8 mPa · s or less. Within this range, the release agent remains on the image surface, which is effective in preventing image loss during storage.

  The viscosity of the release agent at 120 ° C. is measured with an E-type viscometer. For the measurement, an E-type viscometer (manufactured by Tokyo Keiki Co., Ltd.) equipped with an oil circulation type thermostatic bath and a cone plate is used. A cone plate having a cone angle of 1.34 ° is used. A sample is put into the cup, the temperature of the circulation device is set to 120 ° C., an empty measurement cup and cone are placed in the measurement device, and the temperature is kept constant while circulating the oil. When the temperature is stabilized, 1 g of the sample is put in the measuring cup, and the cone is allowed to stand still for 10 minutes. After stabilization, rotate the cone and measure. The rotational speed of the cone is 60 rpm. The measurement is performed three times, and the average value is taken as the melt viscosity.

-Binder resin-
A known binder resin may be used as the binder resin in the toner. The main component of the binder resin is a copolymer of styrene and acrylic acid or methacrylic acid, polyvinyl chloride, phenol resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyolefin resin, polyurethane resin. Polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, polyether polyol resin, etc. are used alone or in combination.
From the viewpoint of durability and the like, a polyester resin, a copolymer of styrene and acrylic acid or methacrylic acid, or a polyolefin resin is preferable, and it is more preferable to use a polyester resin.

The polyester resin suitable for the present embodiment will be further described. The acid component used in the polyester resin includes, for example, terephthalic acid, isophthalic acid, orthophthalic acid, or anhydrides thereof, and preferably terephthalic acid / isophthalic acid. It is an acid. These acid components may be used alone or in combination of two or more.
Furthermore, other acid components may be used in combination with the above acid components. Examples of other acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, and the like. -Butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl Examples also include alkyl or alkenyl succinic acids such as succinic acid, anhydrides of these acids, lower alkyl esters, and other divalent carboxylic acids. Moreover, in order to bridge | crosslink a polyester resin, you may mix a trivalent or more carboxylic acid component as another acid component. Examples of the trivalent or higher carboxylic acid component include 1,2,4-benzenetricarboxylic acid, 1,3,5-benzenetricarboxylic acid, other polycarboxylic acids, and anhydrides thereof.

  Further, in the polyester resin, usually, 80 mol% or more of the alcohol component is composed of a bisphenol A alkylene oxide adduct, desirably 90 mol% or more, and more desirably 95 mol% or more.

  Examples of the bisphenol A alkylene oxide adduct include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4). -Hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, Polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane Etc. These compounds may be used alone or in combination of two or more.

  In the polyester resin used as the binder resin in the present embodiment, other alcohol components may be used in combination with the above alcohol components as necessary. Examples of other alcohol components include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1 , 5-pentanediol, 1,6-hexanediol, diols such as 1,9-nonanediol, and other dihydric alcohols such as bisphenol A and hydrogenated bisphenol A.

  In addition, trihydric or higher alcohols are also suitable as other alcohol components. Examples of the alcohol component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1, Examples include 2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and other trivalent or higher alcohols.

  Further, in the reaction for synthesizing such a polyester resin, in order to accelerate the reaction, a commonly used esterification catalyst such as zinc oxide, stannous oxide, dibutyltin oxide, dibutyltin dilaurate, titanium, etc. is used. used.

  In order to adjust the exposure amount of the release agent on the surface of the black toner, it is preferable to use a release agent having an acid value in the range of 1.0 mgKOH / g. When the release agent particles and the resin particles are agglomerated in a wet state, the release agent enters the aggregated particles if the acid value of the release agent is within the above range. Furthermore, it is more preferable to contain crystalline resin particles in the resin particles. When the crystalline resin particles are mixed in the agglomerated particles, the dispersion unit of the release agent particles can be reduced, and then it becomes easy to coat with the resin particles as a shell.

  The molecular weight of the binder resin is preferably in the range of 1,000 to 100,000 and more preferably in the range of 5,000 to 50,000 as the weight average molecular weight (Mw). The number average molecular weight (Mn) is preferably in the range of 1,000 to 100,000, and more preferably in the range of 2,000 to 50,000.

Here, the molecular weight is measured under the following conditions.
GPC “HLC-8120GPC, SC-8020 (manufactured by Tosoh Corp.)” was used, and the column was “TSKgel, SuperHM-H (6.0 mm ID × 15 cm, manufactured by Tosoh Corp.)”. THF (tetrahydrofuran) is used as the liquid.
As experimental conditions, the sample concentration is 0.5%, the flow rate is 0.6 ml / min, the sample injection amount is 10 μL, the measurement temperature is 40 ° C., and the IR detector is used. The calibration curve is "polystylene standard sample TSK standard" manufactured by Tosoh Corporation: "A-500", "F-1", "F-10", "F-80", "F-380", "A-2500 ”,“ F-4 ”,“ F-40 ”,“ F-128 ”, and“ F-700 ”.
In addition, the molecular weight described in this specification is a value measured by the above method.

  The melting temperature of the binder resin is usually 90 ° C. or higher and 140 ° C. or lower, and the glass transition temperature is 55 ° C. or higher and 70 ° C. or lower.

  The binder resin is preferably contained in the toner particles in an amount of 30% to 95% by weight, more preferably 35% to 90% by weight, and still more preferably 40% to 87% by weight.

-Colorant-
The colorant of the toner particles is not particularly limited as long as it is a known colorant, and may be a dye or a pigment. A pigment is desirable from the viewpoint of light resistance and water resistance.

  Specific examples of the black pigment include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, and magnetite.

  Examples of yellow pigments include yellow lead, zinc yellow, yellow iron oxide, cadmium yellow, chrome yellow, hansa yellow, hansa yellow 10G, benzidine yellow G, benzidine yellow GR, selenium yellow, quinoline yellow, and permanent yellow NCG. Can be given.

  Examples of the orange pigment include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, benzidine orange G, indanthrene brilliant orange RK, indanthrene brilliant orange GK and the like.

  Examples of the red pigment include bengara, cadmium red, red lead, mercury sulfide, watch young red, permanent red 4R, risor red, brilliantamine 3B, brilliantamine 6B, dapon oil red, pyrazolone red, rhodamine B rake, rake. Red C, Rose Bengal, Eoxin Red, Alizarin Lake and the like.

  Blue pigments include, for example, bitumen, cobalt blue, alkali blue lake, Victoria blue lake, fast sky blue, indanthrene blue BC, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite Green ox sale rater. Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.

  Examples of the green pigment include chromium oxide, chrome green, pigment green, malachite green lake, final yellow green G, and the like.

Examples of white pigments include zinc white, titanium oxide, antimony white, and zinc sulfide.
Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, and alumina white.

  Examples of the dye include various dyes such as basic, acidic, dispersed, and direct dyes. Specific examples include nigrosine. Furthermore, these may be used alone, may be used by mixing them, or may be used in a solid solution state.

  These colorants are dispersed by a known method, and for example, a rotary shearing type homogenizer, a media type dispersing machine such as a ball mill, a sand mill, or an attritor, a high pressure opposed collision type dispersing machine or the like is preferably used.

  The colorant of the present embodiment is selected from the viewpoints of hue angle, saturation, brightness, weather resistance, and dispersibility in the toner. As for the addition amount of this coloring agent, it is desirable to add 1 to 20 mass parts with respect to 100 mass parts of resin. It is also effective to use a surface-treated colorant or a pigment dispersant as necessary. By selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  When a magnetic material is used for the black colorant, it is desirable to add 30 to 100 parts by mass with respect to 100 parts by mass of the resin, unlike other colorants.

-Other ingredients-
In addition to the above components, various components such as an internal additive, a charge control agent, inorganic powder (inorganic particles), and organic particles may be added to the toner as necessary.
Examples of the internal additive include metals such as ferrite, magnetite, reduced iron, cobalt, nickel, and manganese, alloys, and magnetic materials such as compounds containing these metals. When the magnetic material is used as a magnetic toner, the ferromagnetic particles preferably have an average particle size of 2 μm or less, more preferably 0.1 μm or more and 0.5 μm or less. The amount to be contained in the toner is preferably 20 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the resin component, and particularly preferably 40 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the resin component. In addition, the magnetic characteristics when applied with 10K oersted are coercive force (Hc) of 20 oersted or more and 300 oersted or less, saturation magnetization (σs) of 50 emu / g or more and 200 emu / g or less, residual magnetization (σr) of 2 emu / g or more and 20 emu / g or less. Things are desirable.

  Examples of the charge control agent include quaternary ammonium salt compounds, nigrosine compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments.

  The toner may contain an inorganic powder for the purpose of adjusting viscoelasticity. Examples of inorganic powders include silica, alumina, titania, calcium carbonate, magnesium carbonate, calcium phosphate, and cerium oxide. Can be mentioned.

  As the external additive externally added to the toner surface, inorganic particles or organic particles are used. Specific examples include the following.

Inorganic particles include silica, alumina, titania, zirconia, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, zinc oxide, titanium oxide, chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, Various inorganic oxides such as tellurium oxide, manganese oxide, boron oxide, silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, boron nitride, nitrides, borides and the like are preferably used.
In order to precisely control charging, it is preferable to use silica and titanium oxide in combination.

  Moreover, titanium coupling agents such as tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzene sulfonyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, γ- (2-amino) Ethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane Hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane The treatment may be performed with a silane coupling agent such as run, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane. Moreover, you may hydrophobize with higher fatty acid metal salts, such as silicone oil, aluminum stearate, zinc stearate, calcium stearate.

The inorganic particles are generally used for the purpose of improving fluidity. The primary particle size of the inorganic particles is preferably 1 nm to 1000 nm, more preferably 5 nm to 800 nm, and even more preferably 5 nm to 700 nm.
In particular, from the viewpoint of powder flowability, charge control, and the like, it is preferable to use inorganic particles having a primary particle size of 40 nm or less. The inorganic particles having such a particle size are subjected to surface treatment, Dispersibility is increased, and the effect of improving powder flowability is increased.
On the other hand, from the viewpoint of adhesive force reduction and charge control, it is preferable to use inorganic particles having a larger diameter.
The amount of inorganic particles added as an external additive is desirably in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the toner.

Organic particles are generally used for the purpose of improving cleaning properties and transfer properties. Specifically, for example, fluorine resin powders such as polyvinylidene fluoride and polytetrafluoroethylene, fatty acid metal salts such as zinc stearate and calcium stearate. , Polystyrene, polymethyl methacrylate and the like.
The average particle diameter of the organic particles is preferably 1 nm to 1000 nm, more preferably 5 nm to 800 nm, and still more preferably 5 nm to 700 nm.

  Other inorganic oxides to be externally added are small-diameter inorganic oxides having a primary particle size of 40 nm or less for powder flowability, charge control, and the like. Large-diameter inorganic oxides are exemplified. From the viewpoint of charge control, it is preferable to use silica and titanium oxide in combination. Further, the surface treatment of the small-diameter inorganic particles increases the dispersibility and increases the effect of improving the powder fluidity.

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

-Toner characteristics-
The volume average particle diameter (D _50T ) of the entire toner is preferably in the range of 3 μm to 8 μm. When _D50T is within the above range, the toner fluidity, chargeability, and resolution are excellent.

The particle diameter is a value obtained by the following measurement method using Coulter Multisizer-II type (manufactured by Beckman-Coulter) and using ISOTON-II (manufactured by Beckman-Coulter) as the electrolyte.
As a dispersant, 1.0 mg of a measurement sample is added to 2 ml of a 5% by mass aqueous solution of sodium alkylbenzenesulfonate, and this is added to 100 ml of the electrolyte to prepare an electrolyte in which the sample is suspended. The electrolyte in which the sample was suspended was dispersed for 1 minute with an ultrasonic disperser, and the particle size distribution of particles from 1 μm to 30 μm was measured with a Coulter Multisizer-II type using an aperture diameter of 50 μm, and the volume Average distribution and number average distribution are obtained. The number of particles to be measured is 50,000.

When the particle to be measured is less than 2 μm, the particle size is measured using a laser diffraction particle size distribution analyzer LA-700 (manufactured by Horiba, Ltd.).
As a measuring method, the sample in the state of dispersion is adjusted so as to have a solid content of 2 g, and ion exchange water is added thereto to make 40 ml. This is put into the cell until an appropriate concentration is reached, and after 2 minutes, the concentration is measured when the concentration in the cell becomes almost stable. The obtained volume average particle diameter for each channel is accumulated from the smaller volume average particle diameter, and the place where the accumulation reaches 50% is defined as the volume average particle diameter.
When measuring powders such as external additives, 2 g of a measurement sample is added to 50 ml of a 5% by mass aqueous solution of sodium alkylbenzenesulfonate, and the sample is dispersed for 2 minutes with an ultrasonic disperser (1000 Hz). Prepared and measured by the same method as the above-mentioned dispersion.

The toner shape factor SF1 is desirably 100 or more and 140 or less. When the shape factor SF1 is within the above range, the transfer efficiency and the image density are improved, so that a high-quality image is formed and a high-gloss image is formed.
Examples of a method for setting the toner shape factor SF1 in the above range include a method for producing a toner by an emulsion aggregation method which is a wet manufacturing method. By manufacturing the toner using a wet manufacturing method such as an emulsion aggregation method, a toner having a shape factor SF1 in the above range is manufactured.

Here, the shape factor SF1 is obtained by the following equation (8).
SF1 = (ML 2 / A) × (π / 4) × 100 (8)
In the above formula (8), ML represents the absolute maximum length of the toner particles, and A represents the projected area of the toner particles.

-Toner production method-
Examples of the toner production method include the following methods.
A kneading and pulverizing method in which a binder resin, a colorant, a release agent, and a charge control agent as necessary are kneaded, pulverized, and classified.
A method of changing the shape of the particles obtained by the kneading and pulverizing method by mechanical impact force or thermal energy.
・ Emulsion polymerization of the polymerizable monomer of the binder resin, and mix the formed dispersion with a dispersion of a colorant, a release agent, and, if necessary, a charge control agent, and agglomerate and heat-fuse. Emulsion polymerization aggregation method to obtain toner particles.
A suspension polymerization method in which a polymerizable monomer for obtaining a binder resin, a colorant, a release agent, and, if necessary, a solution such as a charge control agent are suspended in an aqueous solvent for polymerization.
A dissolution suspension method in which a binder resin, a colorant, a release agent, and, if necessary, a solution such as a charge control agent are suspended in an aqueous solvent and granulated.

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

  From the viewpoints of shape control, particle size distribution control, and wax dispersion structure control in the toner, suspension polymerization method, emulsion polymerization aggregation method, and dissolution suspension method produced with an aqueous solvent are preferable, and emulsion polymerization aggregation method is particularly preferable. For the toner particle production method, for example, the matters described in Japanese Patent No. 3141784 may be applied.

  As described above, with respect to the black toner, it is desirable to adjust the exposure rate of the release agent. To adjust the exposure rate, it is preferable to manufacture the toner based on the following emulsion polymerization method.

That is, it is preferable that the black toner manufacturing method according to the present embodiment includes at least the following steps.
(1) A binder resin particle dispersion adjusting step for adjusting a binder resin particle dispersion in which the binder resin is dispersed.
(2) A colorant particle dispersion adjusting step of adjusting a colorant particle dispersion in which colorant particles are dispersed.
(3) A release agent particle dispersion adjusting step for adjusting a release agent particle dispersion in which a release agent is dispersed.
(4) A mixed solution in which a binder resin particle dispersion, a colorant particle dispersion, and a release agent particle dispersion are mixed to prepare a mixed solution containing the binder resin particles, the colorant particles, and the release agent particles. Adjustment process.
(5) An aggregated particle adjusting step of adjusting aggregated particles in which the binder resin particles, the colorant particles, and the release agent particles are aggregated.
(6) A fusion / union process in which the aggregated particle dispersion in which the aggregated particles are dispersed is heated to a temperature equal to or higher than the glass transition temperature of the binder resin particles.
Furthermore, you may have the process of forming a coating layer by making a resin particle adhere to the surface of an aggregated particle (core particle) after the process of (5) and before the process of (6). By adding this step, a so-called core / shell toner having a shell layer covering the core layer can be obtained.
Such a method for producing a toner by emulsion polymerization makes it easy to control the exposure rate of the release agent on the toner surface.

  Further, as a method for controlling the exposure rate of the release agent to the toner surface, a mixing step of mixing the binder resin particle dispersion and the colorant particle dispersion, and aggregating the binder resin particles and the colorant particles are performed. A first agglomeration step for forming first agglomerated particles; a release agent particle dispersion liquid is mixed with the first agglomerated particles; and the first agglomerated particles and the release agent particles are agglomerated to form a second agglomeration. A toner production method comprising: a second aggregating step for forming particles; and a fusing / merging step for heating and fusing and coalescing the second agglomerated particle dispersion in which the second agglomerated particles are dispersed. Is preferred.

  In this method, the first aggregated particles and the release agent particles are aggregated after forming the first aggregated particles of the binder resin particles and the colorant particles. By such a production method, a release agent can be present which is not easily biased from the surface, on the surface layer of the toner particles, that is, inside the toner and on the toner surface side.

  Further, as a method for controlling the exposure rate of the release agent to the toner surface, it is also preferable to add a crystalline polyester resin to the amorphous polyester resin. By adding the crystalline polyester resin to the amorphous polyester resin, the release agent is guided to the crystalline polyester resin when heated, and the finely dispersed state is maintained and exposed to the toner surface.

  Hereinafter, the production method of the toner according to the exemplary embodiment by the emulsion polymerization method will be described in detail.

(Binder resin particle dispersion adjustment process)
As described above, the binder resin particle dispersion is obtained in the state of resin particle dispersion when the emulsion polymerization method or the like is used in the synthesis of the binder resin.

On the other hand, when a binder resin is obtained by polymerizing in advance by a solution polymerization method or a bulk polymerization method, etc., as described above, the obtained binder resin and a stabilizer are added to a solvent, and mechanically mixed and dispersed. By doing so, a binder resin particle dispersion can be obtained. That is, for example, it is performed by applying a shearing force to a solution obtained by mixing an aqueous medium and a binder resin by a disperser. At that time, particles may be formed by heating to lower the viscosity of the resin component. A dispersant may be used for stabilizing the dispersed resin particles.
Furthermore, if the binder resin is oily and can be dissolved in a solvent having a relatively low solubility in water, the resin is dissolved in those solvents and dispersed in water together with a dispersant and a polymer electrolyte, and then heated or decompressed. Then, the resin particle dispersion may be prepared by evaporating the solvent.

Examples of the disperser include a homogenizer, a homomixer, a pressure kneader, an extruder, and a media disperser.
Examples of the aqueous medium include water such as distilled water and ion-exchanged water; alcohols; and the like.

  Examples of the dispersant include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, and sodium polymethacrylate; sodium dodecylbenzenesulfonate, sodium octadecylsulfate, sodium oleate, Anionic surfactants such as sodium laurate and potassium stearate, cationic surfactants such as laurylamine acetate, stearylamine acetate and lauryltrimethylammonium chloride, zwitterionic surfactants such as lauryldimethylamine oxide, polyoxy Nonio such as ethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine Surfactants such as sex surfactant; and the like are; tricalcium phosphate, aluminum hydroxide, calcium sulfate, calcium carbonate, inorganic salts such as barium carbonate.

  Among the above, it is preferable to use a biodegradable dispersant as the dispersant. However, if the mixed solution contains a biodegradable dispersant, only a dispersant other than the biodegradable dispersant may be used. In addition, a biodegradable dispersant and a dispersant other than the biodegradable dispersant may be used in combination.

  The content of the resin particles contained in the binder resin particle dispersion is preferably in the range of 10% by mass to 50% by mass, and more preferably in the range of 15% by mass to 40% by mass. Within the above range, the particle size distribution becomes narrow and the toner characteristics are excellent.

The volume average particle size of the resin particles in the binder resin particle dispersion is desirably 1 μm or less, and more desirably 0.01 μm or more and 1 μm or less. When the volume average particle size is within the above range, the particle size distribution of the finally obtained toner can be easily adjusted, and deterioration in performance and reliability can be suppressed.
In addition, let the volume average particle diameter of the particle | grains of a dispersion liquid be the value measured using the laser diffraction system particle size distribution measuring apparatus (The Beckman-Coulter company make, LS13320). The obtained volume average particle diameter for each channel is accumulated from the smaller volume average particle diameter, and the place where the accumulation reaches 50% is defined as the volume average particle diameter.

(Colorant particle dispersion adjustment process)
As a method for dispersing the colorant in the solvent, a known method such as a rotary shearing homogenizer, a ball mill having a medium, a sand mill, or a dyno mill is employed.
As a solvent, the aqueous solvent demonstrated with the said resin particle dispersion liquid is mentioned. Examples of the dispersant include the dispersant described in the resin particle dispersion. Examples of the disperser that can be used include those described for the resin particle dispersion.

  The volume average particle diameter of the colorant particles is preferably 0.8 μm or less, and more preferably 0.05 μm or more and 0.5 μm or less. The particle size distribution of the finally obtained toner can be easily adjusted, and the reduction in performance and reliability can be suppressed. Further, toner having a shape control property which is one of the characteristics of the aggregation / unification method and a shape close to a true sphere can be obtained.

(Release agent particle dispersion adjustment process)
The release agent particle dispersion is prepared by dispersing it in the above aqueous solvent together with a polymer electrolyte such as an ionic surfactant, polymer acid, polymer base, etc., heating it above the melting temperature, and applying a strong shearing force. The particles are formed using a homogenizer or a pressure discharge type dispersing machine.
From the viewpoint of controllability of the dispersion structure of the release agent in the toner, the volume average particle size of the release agent dispersion particles in the aqueous dispersion is preferably 50 nm to 500 nm, and preferably 80 nm to 400 nm. More preferred.

  The content of the release agent particles in the release agent particle dispersion is preferably in the range of 3% by mass to 50% by mass, and more preferably in the range of 10% by mass to 40% by mass. Within the above range, the controllability of the release agent dispersion diameter in the toner is excellent.

(Mixed solution adjustment process)
The mixed solution is prepared by mixing the resin particle dispersion, the colorant particle dispersion, and other dispersions such as a release agent particle dispersion as necessary. At this time, the release agent particle dispersion may be added at once in the mixed solution adjustment step, or may be divided and added in multiple stages.

(Aggregated particle adjustment process)
In the aggregated particle adjustment step, the mixed solution is heated to form aggregated particles in which the particles in the mixed solution are aggregated. Note that the heating is desirably performed in a temperature range lower than the melting temperature of the crystalline resin (a temperature lower by 20 ° C. to 10 ° C. than the melting temperature of the crystalline resin).

Aggregated particles are formed by stirring with a rotary shearing homogenizer. Specifically, for example, an aggregating agent is added at 20 ° C. to 30 ° C. to make the pH of the raw material dispersion acidic (eg, pH = 2.8). Is made by
The flocculant used in the agglomerated particle forming step can take a valence of 2 or more in addition to a surfactant having a reverse polarity to the surfactant used as a dispersant added to the raw material dispersion, that is, an inorganic metal salt. A metal complex containing a metal element is preferably used. In particular, the use of a metal complex is particularly preferable because the amount of the surfactant used can be reduced and the charging characteristics are improved.

  Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and inorganic substances such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples thereof include metal salt polymers. Of these, aluminum salts and polymers thereof are particularly preferred. In order to obtain a narrower particle size distribution, the inorganic metal salt is polymerized even if the valence is bivalent rather than monovalent, trivalent than bivalent, tetravalent than trivalent, or the same valence. A type of inorganic metal salt polymer is more suitable.

  Examples of the metal complex containing a metal element capable of taking a valence of 2 or more include a metal salt of aminocarboxylic acid. Specific examples include calcium salts, magnesium salts, iron salts, aluminum salts, and the like based on known chelates such as ethylenediaminetetraacetic acid, propanediaminetetraacetic acid, nitriletriacetic acid, triethylenetetraminehexaacetic acid, diethylenetriaminepentaacetic acid, and the like. It is done.

The inorganic metal salt is preferably dispersed in a solvent to form an inorganic particle dispersion, which is added to the mixed solution in advance in the mixed solution preparation step and simultaneously aggregated. As a result, the inorganic metal salt effectively acts on the molecular chain terminal of the binder resin and contributes to the formation of a crosslinked structure.
The inorganic particle dispersion is prepared using a known method, for example, a ball mill, a sand mill, an ultrasonic disperser rotary shearing homogenizer, or the like, and the dispersion average particle diameter of the inorganic particles is preferably in the range of 100 nm to 500 nm.

  The inorganic particle dispersion may be added stepwise in the aggregated particle forming step, or may be added continuously. These methods are effective in dispersing the metal ion component in the inorganic particle dispersion from the toner surface to the inside. When adding stepwise, it is particularly preferable to add the dispersion at a rate of about 0.1 g / m or less when adding continuously in three steps or more.

  The amount of the inorganic particle dispersion added varies depending on the type of metal required and the degree of formation of the crosslinked structure, but is in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin. It is preferable to set it in a range of 1 part by mass or more and 5 parts by mass or less.

In the agglomerated particle forming step, toner particles are prepared by adjusting the type and amount of inorganic metal salt or metal complex containing a metal element capable of taking a valence of 2 or more in a range that does not affect the formation of agglomerated particles. You may control content of the metal element which can take the valence more than bivalence contained in it.
In addition, from the viewpoint that it is easier to achieve both a low-temperature fixability and a gloss unevenness suppressing effect at a high level, it is preferable to use aluminum sulfate, polyaluminum chloride, or calcium chloride among the aggregating agents listed above. It is.

  The aggregated particle forming step may include an attaching step as necessary. In the attaching step, the coating layer is formed by attaching resin particles to the surface of the aggregated particles (core particles) formed through the above-described aggregated particle forming step. Thus, a toner having a so-called core layer and a core / shell structure covering the core layer is obtained.

  The coating layer is usually formed by additionally adding a resin particle dispersion containing non-crystalline resin particles to the dispersion in which aggregated particles (core particles) are formed in the aggregated particle forming step. In addition, when the amorphous resin is used in addition to the crystalline resin in the step of forming the core particles, the non-crystalline resin used in the adhesion step may be the same as that used in the aggregated particle forming step. It may be.

  In general, the adhesion process is used when a toner having a so-called core / shell structure in which a crystalline resin as a main component is contained as a binder resin together with a release agent, and the main purpose thereof is the core layer. The purpose is to suppress the exposure of the release agent and the crystalline resin contained on the toner surface, and to supplement the strength of the toner particles, which is insufficient with the core layer alone.

(Fusion / unification process)
The fusion and coalescence process, which is performed after the aggregated particle formation process, is adjusted by adjusting the pH of the suspension containing the aggregated particles formed through these processes to stop the progress of aggregation, and then heated. By doing so, the agglomerated particles are fused.

The pH is adjusted by adding an acid and / or alkali. Although an acid is not specifically limited, The aqueous solution which contains inorganic acids, such as hydrochloric acid, nitric acid, and a sulfuric acid, in 0.1 to 50 mass% is preferable. The alkali is not particularly limited, but an aqueous solution containing an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide in the range of 0.1% by mass to 50% by mass is preferable.
In addition, in the adjustment of pH, if a local pH change occurs, local aggregated particles themselves may be destroyed or local excessive aggregation may be caused. In large scale production, it is desirable to prevent over-agglomeration.

  After performing the composition control described above, the aggregated particles are heated and fused. In the fusion, the aggregated particles are fused by heating at a temperature in the range of −10 ° C. to + 20 ° C. from the melting temperature of the release agent particles. Within the above range, the release agent dispersed particle size can be controlled.

The cross-linking reaction may be performed with other components during the heating at the time of fusion or after the fusion is completed. Further, a crosslinking reaction may be performed simultaneously with the fusion. When the crosslinking reaction is performed, the above-described crosslinking agent and polymerization initiator are used in the production of the toner.
The polymerization initiator may be preliminarily mixed with the dispersion at the stage of preparing the raw material dispersion, or may be incorporated into the aggregated particles in the aggregated particle forming step. Furthermore, it may be introduced after the fusion / unification step or after the fusion / unification step. In the case of introduction after the aggregated particle forming step, the adhering step, the fusion / unification step, or the fusion / union step, a solution in which the polymerization initiator is dissolved or emulsified is added to the dispersion. These polymerization initiators may be added with known crosslinking agents, chain transfer agents, polymerization inhibitors and the like for the purpose of controlling the degree of polymerization.

(Washing, drying process, etc.)
After completing the coalescence and coalescence process of the aggregated particles, desired toner particles are obtained through an arbitrary washing process, solid-liquid separation process, and drying process. In the washing process, it is desirable to perform substitution washing with ion-exchanged water in consideration of chargeability. Moreover, although there is no restriction | limiting in particular in a solid-liquid separation process, From the point of productivity, suction filtration, pressure filtration, etc. are suitable. Further, the drying process is not particularly limited, but freeze drying, flash jet drying, fluidized drying, vibration fluidized drying and the like are preferably used from the viewpoint of productivity. Further, the various external additives described above are added to the toner particles after drying as necessary.

<Developer>
The toner according to the exemplary embodiment is used for image formation as a one-component developer or a two-component developer. When used as a two-component developer, it is used by mixing with a carrier.

The carrier for the two-component developer is not particularly limited, and a known carrier is used. Examples thereof include magnetic metals such as iron oxide, nickel and cobalt, magnetic oxides such as ferrite and magnetite, resin-coated carriers having a resin coating layer on the surface of the core material, and magnetic dispersion carriers. Further, a resin-dispersed carrier in which a conductive material or the like is dispersed in a matrix resin may be used.
For manufacturing the carrier, a heating kneader, a heating Henschel mixer, a UM mixer, or the like may be used. Depending on the amount of the coating resin, a heating fluidized rolling bed, a heating kiln, or the like may be used.

  Coating resins and matrix resins used for carriers include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic. Examples include, but are not limited to, an acid copolymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, and an epoxy resin. These resins may be used alone or in combination of two or more.

  Examples of the conductive material include metals such as gold, silver and copper, carbon black, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, and carbon black, but are not limited thereto. It is not something.

Examples of the core material of the carrier include magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. However, in order to use the carrier for the magnetic brush method, it is a magnetic material. It is desirable.
The volume average particle size of the core material of the carrier is generally in the range of 10 μm to 500 μm, and preferably in the range of 30 μm to 100 μm.

  In order to coat the surface of the core material of the carrier with a resin, there may be mentioned a method of coating with a coating layer forming solution prepared by dissolving the coating resin and, if necessary, various additives in an appropriate solvent. The solvent is not particularly limited, and may be selected in consideration of the coating resin to be used, coating suitability, and the like.

Specific resin coating methods include an immersion method in which the carrier core material is immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed onto the surface of the carrier core material, and the carrier core material is fluidized air. A fluidized bed method in which the coating layer forming solution is sprayed in a state of being suspended by the above, a kneader coater method in which the carrier core material and the coating layer forming solution are mixed in a kneader coater, and the solvent is removed.
The amount of the coating resin used is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.5 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the core particles. .

  The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably in the range of toner: carrier = 1: 100 to 30: 100, and more preferably in the range of 3: 100 to 20: 100. .

<Image forming apparatus>
The image forming apparatus of the present embodiment will be described below with reference to the drawings, but the present embodiment is not limited to the following configuration.

In this image forming apparatus, for example, the part including the developing device may have a cartridge structure (process cartridge) that is detachable from the main body of the image forming apparatus. As the process cartridge, a process cartridge that includes at least a developer holder and stores toner according to the present embodiment is used.
Hereinafter, although an example of the image forming apparatus of this embodiment is shown, it is not necessarily limited to this. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

FIG. 1 is a schematic configuration diagram showing a four-tandem color image forming apparatus. The image forming apparatus shown in FIG. 1 is the first of the electrophotographic systems that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K are provided. These image forming units (hereinafter simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed in parallel in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.
In this embodiment, the image forming unit 10K that forms a black image is the first image forming unit, and the image forming units 10Y, 10M, and 10C that form images of colors other than black are the second image forming units. A unit. The second image forming unit may have at least one of 10Y, 10M, and 10C.

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

  The image forming apparatus shown in FIG. 1 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K are attached to and detached from each other. The developing devices 4Y, 4M, 4C, and 4K each have their respective developing devices (colors). And a toner supply pipe (not shown). Further, when the amount of toner stored in the toner cartridge is low, this toner cartridge may be replaced.

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

The first unit 10Y has a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, a charging roller 2Y that charges the surface of the photoreceptor 1Y, and an exposure apparatus 3 that forms an electrostatic latent image by exposing the charged surface with a laser beam 3Y based on the color-separated image signal. A developing device 4Y that supplies the electrostatic latent image with charged toner to develop the electrostatic latent image, a primary transfer roller 5Y (primary transfer device) that transfers the developed toner image onto the intermediate transfer belt 20, and A photoconductor cleaning device 6Y for removing toner remaining on the surface of the photoconductor 1Y after the primary transfer is sequentially provided.
The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rollers 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

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

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

  In the developing device 4Y, for example, yellow toner containing at least a yellow colorant, a binder resin, and a release agent is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoreceptor 1Y on which the yellow toner image is formed continues to run, and the toner image developed on the photoreceptor 1Y is conveyed to the primary transfer position.

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

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

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

Thereafter, the recording paper P is fed into the fixing device 28, the toner image is heated, and the color-superposed toner image is melted and fixed on the recording paper P. The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.
The image forming apparatus exemplified above is configured to transfer the toner image onto the recording paper P via the intermediate transfer belt 20, but the present invention is not limited to this configuration, and the toner image is directly transferred from the photoconductor. It may be a structure that is transferred to a recording sheet.

  Next, the image forming apparatus of this embodiment will be described. In the image forming apparatus according to the present exemplary embodiment, the black toner and the other color toner are stored in the developing device. It should be noted that at least the toner may be accommodated in the image forming apparatus of the present embodiment, and for example, a developer may be accommodated depending on the mechanism of the image forming apparatus.

<Toner set>
The toner set of this embodiment includes a black toner containing at least a black colorant, a binder resin, and a release agent, and a non-black color containing at least a colorant other than black, a binder resin, and a release agent. Color toner (other color toner). The melting temperature of the release agent contained in the black toner is 3 ° C. or more lower than the melting temperature of the release agent contained in the toner of a color other than black.
As described above, the black toner and the other color toner may further contain silica, a charge control agent, and an external additive. The preferred range of black toner and other color toner is as described above. As described above, the black toner and the other color toner in the toner set are used as a one-component developer or a two-component developer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples at all. In the following description, “part” and “%” are all based on mass unless otherwise specified.

[Example 1]
<Synthesis of Crystalline Polyester Resin Emulsion A>
(Synthesis of polyester resin emulsion A)
97 parts of dimethyl terephthalate, 97 parts of dimethyl isophthalate, 240 parts of bisphenol A propylene oxide adduct, 32 parts of 1,9 nonanediol and 0.12 part of dibutyltin oxide were stirred at 180 ° C. for 7 hours under a nitrogen atmosphere. Then, after stirring for 3 hours under reduced pressure, 8 parts of trimellitic anhydride was added and further stirred for 2 hours to obtain a polyester resin having a weight average molecular weight Mw = 31200 and a number average molecular weight Mn = 7100. The glass transition point was 59 ° C. Further, 50 parts of this resin was dissolved in 250 parts of ethyl acetate, a solution obtained by dissolving 2 parts of the anionic surfactant Dowfax in 300 parts of ion-exchanged water was added, and the mixture was stirred at 8000 rpm for 10 minutes using a homogenizer (Ultra Turrax). After that, ethyl acetate was removed to obtain a polyester resin emulsion A having a volume average particle size of 0.20 μm.

(Adjustment of colorant particle dispersion Bk)
Carbon black R330 (50 parts), ionic surfactant Neogen RK (4 parts), ion-exchanged water (250 parts) are mixed, dispersed for 10 minutes with a homogenizer, and then irradiated with an ultrasonic disperser for 1 hour. A colorant particle dispersion Bk in which colorant particles having an average diameter of 170 nm were dispersed was obtained.

(Adjustment of colorant particle dispersion C)
Colorant particle dispersion C in which colorant particles having a volume average diameter of 190 nm were dispersed was obtained in the same manner except that Cyan pigment B15: 3 was used instead of carbon black R330.

(Adjustment of colorant particle dispersion M)
Colorant particle dispersion M in which colorant particles having a volume average diameter of 210 nm were dispersed was obtained in the same manner except that Magenta pigment R122 was used instead of carbon black R330.

(Adjustment of colorant particle dispersion Y)
Colorant particle dispersion Y in which colorant particles having a volume average diameter of 185 nm were dispersed was obtained in the same manner except that Yellow pigment Y180 was used instead of carbon black R330.

(Preparation of release agent particle dispersion A)
Fischer-Tropsch wax (melting temperature: 90 ° C., molecular weight: 610) 50 parts, ionic surfactant (Neogen RK) 5 parts, ion-exchanged water 200 parts are mixed, heated to 95 ° C., dispersed with a homogenizer, A release agent particle dispersion A (solid content: 25% by mass) in which release agent particles having a volume average particle size of 230 nm were dispersed was obtained by dispersion treatment with a pressure discharge type gorin homogenizer.

(Adjustment of release agent particle dispersion B)
Fischer-Tropsch wax (melting temperature: 82 ° C., molecular weight: 545) 50 parts, ionic surfactant (Neogen RK) 5 parts, ion-exchanged water 200 parts are mixed, heated to 95 ° C., dispersed with a homogenizer, A release agent particle dispersion B (solid content: 25% by mass) in which release agent particles having a volume average particle size of 205 nm were dispersed was obtained by dispersion treatment using a pressure discharge type gorin homogenizer.

(Preparation of toner particles C1)
700 parts of polyester resin emulsion A, 40 parts of release agent particle dispersion A, 100 parts of ion exchange water, 25 parts of colorant particle dispersion C, 1.5 parts of 10 mass% polyaluminum chloride aqueous solution (manufactured by Asada Chemical Co., Ltd.) are round. After mixing and dispersing in a stainless steel flask with a homogenizer (manufactured by IKA, Ultra Tarrax T50), the contents in the flask were heated and stirred to 45 ° C. while stirring, and then held for 30 minutes.

Next, 300 parts of an additional polyester resin emulsion A was added, and the temperature of the resulting contents was gradually raised to 52 ° C. The particle diameter at this time was 6.6 μm when measured with a Coulter counter (manufactured by Beckman Coulter).
Thereafter, the pH is adjusted to 8 with an aqueous sodium hydroxide solution, the temperature is raised to 95 ° C., and the aggregates are coalesced over 5 hours, and then cooled, filtered, and washed with ion-exchanged water. Then, solid-liquid separation was performed with a suction filter.
Further, it was redispersed in 3 L of ion exchange water at 30 ° C., and stirred and washed at 300 rpm for 15 minutes. This was repeated five more times, and when the electrical conductivity of the filtrate reached 12 μS / cm, solid-liquid separation was performed, and then dried in a vacuum dryer for 12 hours. When the particle diameter of the obtained toner particles C1 was measured with a Coulter counter, the volume average particle diameter was 6.4 μm, and the melting temperature of the release agent in the toner was 89.5 ° C. from thermal analysis.

(Preparation of toner particles M1, Y1)
Toner particles M1 and Y1 were obtained in the same manner as the toner particles C1 except that the colorant particle dispersions M and Y were used in place of the colorant particle dispersion C, respectively. The respective volume average particle diameters were M1 of 6.3 μm and Y1 of 6.6 μm. From the thermal analysis, the melting temperature of the release agent in the toner was 89.4 ° C. and 90.1 ° C., respectively.

(Preparation of toner particles Bk1)
Toner particles are prepared in the same manner as the toner particles C1 except that the colorant particle dispersion Bk is used instead of the colorant particle dispersion C, and the release agent particle dispersion B is used instead of the release agent particle dispersion A. Bk1 was obtained. The volume average particle diameter was 6.5 μm, and the melting temperature of the release agent in the toner was 81.6 ° C. from thermal analysis.

(Carrier adjustment)
Cu-Zn-ferrite (average particle size 40 μm), 0.8 mass% silicone resin (trade name: SR2411, solid content 20 mass%, manufactured by Toray Dow Corning Silicone Co., Ltd.) is heated and decompressed with a 5 L kneader device. Then, after cooling, it was sieved with an aperture of 106 μm to prepare a carrier.

(Adjustment of toners C1, M1, Y1, Bk1, developer C1, M1, Y1, Bk1)
Titanium oxide (average particle size 20 nm, anatase type) hydrophobized with n-decyltrimethoxysilane to the toner particles C1 is 0.8 parts with respect to 100 parts of toner, and silica hydrophobized with silicone oil ( 1.0 part of an average particle size of 40 nm, gas phase method) was added, mixed for 15 minutes with a 5 L Henschel mixer, and sieved with a vibrating sieve with an aperture of 106 μm to obtain toner C1.
Further, 8 parts of toner C1 was mixed with 100 parts of the obtained carrier by a V-type blender to obtain developer C1.

  Toners M1, Y1, Bk1, and further developers M1, Y1, Bk1 were obtained in the same manner as toner C1, developer C1, except that M1, Y1, Bk1 were used instead of toner particles C1, respectively.

<Evaluation>
(Evaluation of image defect)
Using a modified ApeosPortIII C7600 manufactured by Fuji Xerox Co., Ltd., a solid patch image (4 cm × 4) on one sheet of recording paper (SP paper A4, basis weight 60 g / cm ² manufactured by Fuji Xerox Co., Ltd.) with developer C1, M1, Y1. 5cm) is fixed by increasing the fixing temperature from 130 ° C. by 5 ° C., and the minimum fixing temperature is obtained from a bending test. At the setting fixing temperature of + 10 ° C. from the minimum fixing temperature, half of the process direction is color 3 Solid color image, the other half is one solid patch image (4cm × 5cm) with developer C1, M1, Y1 and a character image with developer Bk. The 20th solid patch and the black character image are each cut into a size of 6 cm × 6 cm. The cut solid patches and character images were overlapped with the printed parts facing each other, and a 2 kg weight was placed and stored in a chamber at 55 ° C. and 50 RH% for 1 month. And evaluated.

Thereafter, the superimposed images were peeled off to confirm the loss of the character image. The evaluation results are shown in Table 1.
The evaluation criteria are as follows. If ◎ or ○, there is no practical problem, and Δ indicates a level that may cause a problem when a special image is output.

A: Character image defect is not observed.
○: Some loss of character image is seen, but practically no problem.
[Delta]: A level where there are defects in the character image and there are parts that are difficult to see in the fine line image.
X: Character image loss is remarkable, causing a problem in practical use.

(Measurement of exposure rate of release agent on toner surface)
The exposure rate of the release agent on the black toner surface was measured by X-ray photoelectron spectroscopy (XPS). The measurement results are shown in Table 1.

(Evaluation of image quality)
The image quality of the first printed image in the image defect evaluation was evaluated according to the following criteria.

A: The black character image and the solid image are extremely good with no blurring or flickering.
○: Black character image and solid image are good without occurrence of faintness or flickering.
Δ: Black character image may be blurred or flickering but acceptable.
×: There is a jump in the black text image and there is a problem in image quality

[Example 2]
(Preparation of release agent particle dispersion C)
Similar to the release agent particle dispersion B in Example 1, except that Fischer-Tropsch wax (melting temperature: 82 ° C., molecular weight: 545) was used, but polyethylene wax (melting temperature: 86 ° C., molecular weight: 530) Instead of, release agent particle dispersion C (solid content: 25% by mass) was obtained.

(Production of toner particles Bk2, toner Bk2, developer Bk2)
The toner particles Bk2 were produced in the same manner as in the production of the toner particles Bk1 of Example 1, except that the release agent particle dispersion B was replaced with the release agent particle dispersion C. Using this toner particle Bk2, toner Bk2 and developer Bk2 were prepared in the same manner as in Example 1.

(Evaluation)
The exposure rate was measured and image defects and image quality were evaluated in the same manner as in the examples. The results are shown in Table 1.

[Example 3]
(Preparation of release agent particle dispersion D)
Similar to the release agent particle dispersion B of Example 1, except that Fischer-Tropsch wax (melting temperature: 77 ° C., molecular weight: 530) was used, paraffin wax (melting temperature: 76 ° C., molecular weight: 530) Instead, release agent particle dispersion D (solid content: 25% by mass) was obtained.

(Production of toner particles Bk3, toner Bk3, developer Bk3)
As in the preparation of the toner particles Bk1 of Example 1, except that the release agent particle dispersion B is replaced with the release agent particle dispersion D, and the coalescence temperature is changed from 95 ° C. to 85 ° C. Particle Bk3 was produced. Using this toner particle Bk3, toner Bk3 and developer Bk3 were produced in the same manner as in Example 1.

(Evaluation)
The exposure rate was measured and image defects and image quality were evaluated in the same manner as in the examples. The results are shown in Table 1.

[Example 4]
(Preparation of release agent particle dispersion E)
Similar to the release agent particle dispersion B in Example 1, except that Fischer-Tropsch wax (melting temperature: 77 ° C., molecular weight: 530) was used, paraffin wax (melting temperature: 73 ° C., molecular weight: 510) Instead of, release agent particle dispersion E (solid content: 25% by mass) was obtained.

(Preparation of toner particles Bk4, toner Bk4, developer Bk4)
As in the preparation of the toner particles Bk1 of Example 1, except that the release agent particle dispersion B is replaced with the release agent particle dispersion E, and the coalescence temperature is changed from 95 ° C. to 85 ° C. Particle Bk4 was produced. Using this toner particle Bk4, a toner Bk4 and a developer Bk4 were produced in the same manner as in Example 1.

(Evaluation)
The exposure rate was measured and image defects and image quality were evaluated in the same manner as in the examples. The results are shown in Table 1.

[Example 5]
(Production of toner particles Bk5, toner Bk5, developer Bk5)
In the same manner as in the production of the toner particles Bk3 of Example 3, except that 800 parts are used instead of 700 parts of the first polyester resin emulsion A and 200 parts instead of 300 parts of the additional polyester resin emulsion A. The coalescence temperature was changed from 85 ° C. to 95 ° C. to produce toner particles Bk5. Using this toner particle Bk5, toner Bk5 and developer Bk5 were produced in the same manner as in Example 1.

(Evaluation)
The exposure rate was measured and image defects and image quality were evaluated in the same manner as in the examples. The results are shown in Table 1.

[Comparative Example 1]
(Adjustment of toner particles Bk10)
The toner particles Bk10 were obtained in the same manner as in the production of the toner particles Bk1, except that the release agent particle dispersion B was used instead of the release agent particle dispersion A. The volume average particle diameter of the toner particles Bk10 is 6.3 μm, and the melting temperature of the release agent in the toner is 90.2 ° C. from thermal analysis.

(Adjustment of toner Bk10 and developer Bk10)
Toner Bk10 and developer Bk10 were obtained in the same manner as toner Bk1 and developer Bk1, except that toner particle Bk10 was used instead of toner particle Bk1.

[Comparative Example 2]
(Preparation of release agent particle dispersion F)
Similar to the release agent particle dispersion B of Example 1, except that Fischer-Tropsch wax (melting temperature: 82 ° C., molecular weight: 545) was used, but paraffin wax (melting temperature: 88 ° C., molecular weight: 570). Instead of, release agent particle dispersion F (solid content: 25% by mass) was obtained.

(Preparation of toner particles Bk11, toner Bk12, developer Bk12)
In the same manner as in the production of the toner particles Bk1 of Example 1, except that the release agent particle dispersion B is replaced with the release agent particle dispersion F, thereby producing toner particles Bk12. Using this toner particle Bk12, a toner Bk12 and a developer Bk12 were produced in the same manner as in Example 1.

(Evaluation)
The exposure rate was measured and image defects were evaluated in the same manner as in the examples. The results are shown in Table 1.

As shown in Table 1, in Examples 1 to 5, the melting temperature of the release agent contained in the black toner is 3 ° C. or lower than the melting temperature of the release agent contained in the other color toner. It can be seen that the loss of the character image is remarkably suppressed as compared with Comparative Examples 1 and 2 in which the difference in melting temperature of the agent is less than 3 ° C.
Further, in Examples 1 to 4 in which the exposure rate of the release agent on the black toner surface was 0 atm% or more and 20 atm% or less, the occurrence of character image defects was suppressed, and an image with excellent image quality was obtained. .

1Y, 1M, 1C, 1K photoconductor (latent image carrier)
2Y, 2M, 2C, 2K charging roller 3Y, 3M, 3C, 3K laser beam (electrostatic latent image forming device)
3 Exposure equipment
4Y, 4M, 4C, 4K Developing devices 5Y, 5M, 5C, 5K Primary transfer rollers 6Y, 6M, 6C, 6K Photoconductor cleaning devices 8Y, 8M, 8C, 8K Toner cartridges 10Y, 10M, 10C, 10K Unit 20 Intermediate Transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer roller (transfer device)
28 Fixing device 30 Intermediate transfer member cleaning device P Recording paper (transfer object)

Claims (4)

A first image forming unit that forms a black toner image with black toner;
A second image forming unit that forms a toner image of a different color with toner of a color other than black;
Have
Each of the black toner and the non-black toner contains at least a colorant, a binder resin, and a release agent, and the melting temperature of the release agent contained in the black toner is contained in a toner other than black. An image forming apparatus that is 3 ° C. or more lower than the melting temperature of the release agent.   The image forming apparatus according to claim 1, wherein a melting temperature of the release agent for the black toner is 75 ° C. or higher, and a melting temperature of the release agent contained in the toner of a color other than black is 80 ° C. or higher. .   The image forming apparatus according to claim 1, wherein an exposure rate of the release agent on the surface of the black toner is 0 atm% or more and 20 atm% or less. A black toner containing at least a black colorant, a binder resin and a release agent;
A toner of a color other than black containing at least a colorant other than black, a binder resin and a release agent,
A toner set in which the melting temperature of the release agent contained in the black toner is lower by 3 ° C. or more than the melting temperature of the release agent contained in the toner of a color other than black.