JP2018040901A - Toner set for electrostatic charge image development, toner cartridge, electrostatic charge image developer set, image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, in an image forming apparatus comprising four image holding bodies, two primary intermediate transfer bodies, and one secondary intermediate transfer body, a toner set for electrostatic charge image development that reduces the occurrence of streak-like density unevenness in an image formed by the third image holding body.SOLUTION: A toner set for electrostatic charge image development includes a first toner, a second toner, a third toner, and a fourth toner including toner particles and titanium oxide particles externally added to each of the toner particles. The ratio of concentration of titanium between the first to fourth toners is as follows. The first toner: second toner: third toner: fourth toner=1.6 to 1.9:2.0 to 2.4:1.2 to 1.5:0.5 to 1.1.SELECTED DRAWING: Figure 1

Description

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

  Patent Document 1 discloses a four-color toner set in which each toner contains silica and titanium oxide as external additives, and the amount of charge before adding the external additive is lower than that of other toners. A toner set is disclosed in which the titanium oxide ratio is greater than the silica / titanium oxide ratio in other toners.

  In Patent Document 2, as external additives, hydrophobic silica particles having a number average particle diameter of 5 to 20 nm, particles selected from hydrophobic titania and silica having a number average particle diameter of 20 to 100 nm, silica and magnesia are disclosed. A toner containing composite oxide particles having an average primary particle diameter of 0.01 to 0.5 μm is disclosed.

  In Patent Document 3, as external additives, silica particles, and surface-modified silica particles in which the surface of the silica particles is modified with an oxide or hydroxide of at least one metal selected from titanium, tin, zirconium and aluminum; And a toner containing 1.5 times or less by weight of the surface-modified silica particles with respect to the silica particles.

JP 2006-039229 A JP 2007-218941 A JP 2004-093735 A

An image forming apparatus comprising four image carriers, two primary intermediate transfer members, and one secondary intermediate transfer member,
A second image carrier from the upstream side in the rotational direction of the first intermediate transfer member to a first intermediate transfer member, which is a primary intermediate transfer member to which a toner image is transferred from the first image carrier and the second image carrier; These two image carriers are in contact with each other in the order of the first image carrier,
From the upstream side in the rotational direction of the second intermediate transfer member to the second intermediate transfer member, which is a primary intermediate transfer member to which the toner image is transferred from the third image carrier and the fourth image carrier, These two image carriers are in contact in the order of the third image carrier,
From the upstream side in the rotational direction of the third intermediate transfer member, the first intermediate transfer member is transferred from the first intermediate transfer member to the third intermediate transfer member, which is a secondary intermediate transfer member to which the toner image is transferred from the first intermediate transfer member and the second intermediate transfer member. In the image forming apparatus in which the two primary intermediate transfer members are in contact with each other in the order of the second intermediate transfer member,
Streaky density unevenness may occur in the image formed by the third image carrier.

  According to the present invention, the third image holding is performed in the image forming apparatus having the above configuration as compared with the case where the titanium concentration ratio of the first to fourth toners is 1.0: 1.0: 1.0: 1.0. It is an object of the present invention to provide a toner set for developing an electrostatic image that suppresses the occurrence of streaky density unevenness in an image formed by a body.

  Specific means for solving the above-described problems include the following modes.

The invention according to claim 1
A first toner, a second toner, a third toner, and a fourth toner containing toner particles and titanium oxide particles externally added to the toner particles;
The titanium concentration ratio of the first to fourth toners is as follows: first toner: second toner: third toner: fourth toner = 1.6 to 1.9: 2.0 to 2.4: 1.2 to 1. .5: Toner set for developing an electrostatic charge image of 0.5 to 1.1.

The invention according to claim 2
The toner set for developing electrostatic images according to claim 1, wherein the titanium oxide particles are particles containing at least one of titanium oxide and metatitanic acid.

The invention according to claim 3
Containing the toner set for developing an electrostatic charge image according to claim 1,
A toner cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 4
A first developer, a second developer, a third developer, and a fourth developer, including toner containing toner particles and titanium oxide particles externally added to the toner particles;
The titanium concentration ratio of the toner contained in the first to fourth developers is as follows: first developer: second developer: third developer: fourth developer = 1.6 to 1.9: 2.0 to 2.4: The electrostatic charge image developer set which is 1.2 to 1.5: 0.5 to 1.1.

The invention according to claim 5
The electrostatic charge image developer set according to claim 4, wherein the titanium oxide particles are particles containing at least one of titanium oxide and metatitanic acid.

The invention according to claim 6
A first image carrier, a second image carrier, a third image carrier, a fourth image carrier,
First charging means for charging the surface of the first image carrier, second charging means for charging the surface of the second image carrier, and third charging means for charging the surface of the third image carrier. A fourth charging means for charging the surface of the fourth image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged first image carrier, the charged second image carrier, the charged third image carrier, and the charged fourth image carrier. When,
First developing means for containing a first developer and developing the electrostatic image formed on the surface of the first image carrier as a toner image by the first developer;
Second developing means for containing a second developer and developing the electrostatic image formed on the surface of the second image carrier as a toner image by the second developer;
Third developing means for containing a third developer and developing an electrostatic charge image formed on the surface of the third image carrier as a toner image by the third developer;
Fourth developing means for containing a fourth developer, and developing the electrostatic image formed on the surface of the fourth image carrier as a toner image by the fourth developer;
A primary intermediate transfer body to which a toner image is transferred from the first image holding body and the second image holding body, wherein the second image holding body and the first image transfer body from the upstream side in the rotation direction of the primary intermediate transfer body. A first intermediate transfer member in contact with these image carriers in the order of the image carrier;
A primary intermediate transfer body to which a toner image is transferred from the third image holding body and the fourth image holding body, wherein the fourth image holding body and the third image transfer body from the upstream side in the rotation direction of the primary intermediate transfer body; A second intermediate transfer member in contact with these image carriers in the order of the image carriers;
A secondary intermediate transfer body to which a toner image is transferred from the first intermediate transfer body and the second intermediate transfer body, the first intermediate transfer body from the upstream side in the rotation direction of the secondary intermediate transfer body; A third intermediate transfer member in contact with these primary intermediate transfer members in the order of the second intermediate transfer member;
Transfer means for transferring the toner image transferred to the surface of the third intermediate transfer member to the surface of the recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
A first cleaning means for cleaning toner remaining on the surface of the first image carrier after transferring the toner image;
A second cleaning means for cleaning toner remaining on the surface of the second image carrier after transferring the toner image;
A third cleaning means for cleaning toner remaining on the surface of the third image carrier after transferring the toner image;
A fourth cleaning means for cleaning the toner remaining on the surface of the fourth image carrier after transferring the toner image;
With
Each of the first developer, the second developer, the third developer, and the fourth developer includes toner containing toner particles and titanium oxide particles externally added to the toner particles; The titanium concentration ratio of the toner contained in the first to fourth developers is the first developer: second developer: third developer: fourth developer = 1.6 to 1.9: 2.0 to 2 .4: 1.2 to 1.5: 0.5 to 1.1,
Image forming apparatus.

The invention according to claim 7 provides:
An image forming method for forming an image on a recording medium using the image forming apparatus according to claim 6.

  According to the first and second aspects of the invention, the image having the above-described configuration is compared with the case where the titanium concentration ratio of the first to fourth toners is 1.0: 1.0: 1.0: 1.0. In the forming apparatus, there is provided a toner set for developing an electrostatic charge image that suppresses generation of streaky density unevenness in an image formed by a third image carrier.

  According to the third aspect of the present invention, the image forming apparatus having the above-described configuration is compared with the case where the titanium concentration ratio of the first to fourth toners is 1.0: 1.0: 1.0: 1.0. The toner cartridge for suppressing the occurrence of streaky density unevenness in the image formed by the third image carrier is provided.

  According to the fourth and fifth aspects of the invention, the titanium concentration ratio of the toner contained in the first to fourth developers is 1.0: 1.0: 1.0: 1.0 as compared with the case where the titanium concentration ratio is 1.0: 1.0: 1.0: 1.0. In the image forming apparatus having the configuration described above, an electrostatic charge image developer set that suppresses the occurrence of streaky density unevenness in the image formed by the third image carrier is provided.

  According to the sixth and seventh aspects of the invention, compared with the case where the titanium concentration ratio of the toner contained in the first to fourth developers is 1.0: 1.0: 1.0: 1.0, Provided are an image forming apparatus and an image forming method for suppressing generation of streaky density unevenness in an image formed by a three-image holding member.

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

  Embodiments of the invention will be described below. These descriptions and examples illustrate embodiments and do not limit the scope of the invention.

  In the present disclosure, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, the plurality of the substances present in the composition unless otherwise specified. It means the total amount of substance.

  In the present disclosure, “(meth) acryl” means that either “acryl” or “methacryl” may be used.

  In the present disclosure, the “electrostatic image developer” is also simply referred to as “developer”.

<Toner set for developing electrostatic image>
The electrostatic image developing toner set (hereinafter also referred to as “toner set”) according to the present embodiment includes toner particles and titanium oxide particles externally added to the toner particles. A toner, a third toner, and a fourth toner, and the titanium concentration ratio of the first to fourth toners is: first toner: second toner: third toner: fourth toner = 1.6 to 1.9: 2 0.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1.

In this embodiment, the titanium concentration ratio of the first to fourth toners is obtained by fluorescent X-ray analysis. Specifically, it is determined by the following method using a fluorescent X-ray analyzer (for example, XRF-1500 manufactured by Shimadzu Corporation).
Standard toner in which titanium oxide particles (TiO ₂ , for example, volume average particle diameter 50 nm) are externally added to resin particles (for example, volume average particle diameter 6.0 μm) made only of resin (for example, polyester resin) by changing the amount of external addition. A sample is prepared, the X-ray intensity of Ti is measured, and a calibration curve of titanium element concentration (mass%) is created. The X-ray intensity of Ti is measured for the first to fourth toners that are test samples, and the X-ray intensity of Ti is converted into a titanium element concentration by applying to the calibration curve, and the titanium concentration ratio between the toners from this titanium element concentration Is calculated. Without preparing a calibration curve for the standard toner sample, the X-ray intensity of Ti may be measured for the first to fourth toners, and the X-ray intensity ratio between the toners may be the titanium concentration ratio.
As for the toner contained in the developer, the toner and the carrier are separated by blow-off, and the separated toner is used as a test sample.

The toner set according to this embodiment is
An image forming apparatus comprising four image carriers, two primary intermediate transfer members, and one secondary intermediate transfer member,
A second image carrier from the upstream side in the rotational direction of the first intermediate transfer member to a first intermediate transfer member, which is a primary intermediate transfer member to which a toner image is transferred from the first image carrier and the second image carrier; These two image carriers are in contact with each other in the order of the first image carrier,
From the upstream side in the rotational direction of the second intermediate transfer member to the second intermediate transfer member, which is a primary intermediate transfer member to which the toner image is transferred from the third image carrier and the fourth image carrier, These two image carriers are in contact in the order of the third image carrier,
From the upstream side in the rotational direction of the third intermediate transfer member, the first intermediate transfer member is transferred from the first intermediate transfer member to the third intermediate transfer member, which is a secondary intermediate transfer member to which the toner image is transferred from the first intermediate transfer member and the second intermediate transfer member. In the image forming apparatus in which the two primary intermediate transfer members are in contact with each other in the order of the second intermediate transfer member,
Occurrence of streaky density unevenness in an image formed by the third image carrier is suppressed.

  In the image forming apparatus having the above configuration, when the surfaces of the four image carriers are cleaned by the respective cleaning units, the first image carrier, the second image carrier, and the fourth image carrier are compared with each other. In the three-image holding member, a phenomenon (filming) in which the toner is fixed and becomes a film tends to occur. As a result, the surface potential of the third image carrier is lowered and the amount of toner attached to the electrostatic charge image is reduced, so that streaky density unevenness may occur in the image formed by the third image carrier. The following is presumed as a mechanism in which filming is likely to occur in the third image carrier.

In the image forming apparatus having the above configuration, if the image carrier, the primary intermediate transfer member, and the secondary intermediate transfer member continue to rotate, at least the toner remaining on the secondary intermediate transfer member without being transferred to the recording medium. Part of the toner transferred to the primary intermediate transfer member, and at least part of the toner transferred from the secondary intermediate transfer member to the primary intermediate transfer member, and remained on the primary intermediate transfer member without being transferred to the secondary intermediate transfer member At least part of the toner is transferred to the image carrier. At this time, transition is made to four image carriers in accordance with the contact order of one secondary intermediate transfer member and two primary intermediate transfer members and the contact order of one primary intermediate transfer member and two image carriers. It is estimated that the amount of toner is different.
That is, more toner is transferred to the first intermediate transfer member that comes into contact with the secondary intermediate transfer member first, and the first intermediate transfer member comes into contact with the primary intermediate transfer member first. More toner is transferred to the image carrier (the second image carrier for the first intermediate transfer member and the fourth image carrier for the second intermediate transfer member). The amount of toner transferred from the first to the fourth image carrier is estimated to be in the order of 2> 1 ≧ 4> 3.
If the amount of toner transferred from the intermediate transfer member to the image holding member is relatively small, the pressure applied to one toner when the cleaning unit cleans the image holding member becomes relatively high. It is presumed that filming is likely to occur on the surface of the third image carrier with a small amount of toner transferred from the intermediate transfer member compared to the first image carrier, the second image carrier and the fourth image carrier. . In the first image carrier, the second image carrier, and the fourth image carrier, the amount of toner transferred from the intermediate transfer member is ensured to some extent, and the pressure of the cleaning unit for each toner is dispersed, so that filming occurs. It is presumed that filming is unlikely to occur because the toner hardly aggregates or the amount of toner transferred from the intermediate transfer member is large and the toner aggregates to form a toner lump and contacts the cleaning means as the toner lump. Toner filming is likely to occur when images are continuously formed in an environment of low temperature and low humidity (for example, a temperature of 10 ° C. and a relative humidity of 10%).

  In response to the above event, the toner set according to the present embodiment has a titanium concentration ratio of the first to fourth toners, and the first toner: second toner: third toner: fourth toner = 1.6 to 1.9. : 2.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1, and when applied to the image forming apparatus having the above configuration, the first toner is used as the first image carrier. And the second toner is used for the second image carrier, the third toner is used for the third image carrier, and the fourth toner is used for the fourth image carrier. As a result, the occurrence of streaky density unevenness in the image formed by the third image carrier is suppressed. The reason why the toner set according to this embodiment employs the above configuration is as follows.

Since titanium oxide has a low electric resistance, it has a function of attenuating the charging of the toner. Therefore, the higher the content of titanium oxide, the smaller the charge amount of the toner. On the other hand, as the amount of charge increases, the toner is more difficult to be transferred and more likely to remain on the image carrier and more difficult to be removed by the cleaning means. Therefore, it can be said that the toner is more likely to remain on the image carrier as the titanium oxide content is lower (in other words, the toner content is less likely to remain on the image carrier as the titanium oxide content is higher).
Therefore, first, the order of the amount of toner remaining on the image carrier without being transferred to the primary intermediate transfer member is set in correspondence with the order of the amount of toner transferred from the intermediate transfer member to the first, second, and fourth image carriers. In order to control, the titanium concentrations of the first, second, and fourth toners are set in the order of the second toner, the first toner, and the fourth toner from the highest.
Next, as the third toner, since the third image carrier has the smallest amount of toner transferred from the intermediate transfer member, the titanium concentration of the third toner is set to maximize the amount of toner remaining on the image carrier. Is considered to be the lowest. However, considering that the toner remaining on the fourth image carrier is transferred to the third image carrier on the primary intermediate transfer member, the first to fourth toners are made to have the lowest titanium concentration in the third toner. When the titanium concentration of the toner is 2>1>4> 3, the amount of toner present on the third image carrier (the amount of toner remaining on the third image carrier and the amount of toner transferred from the intermediate transfer member) And the amount of toner transferred from the fourth image carrier onto the primary intermediate transfer member) becomes excessive, and the third image carrier is fogged on the image recording surface on which an image is formed (the electrostatic charge of the image carrier). In some cases, toner may adhere to a portion where there is no image and an image appears. From the viewpoint of preventing fogging while suppressing image density unevenness due to toner filming, the titanium concentration of the third toner is made higher than the titanium concentration of the fourth toner.
Therefore, the titanium concentrations of the first to fourth toners are set in the order of 2>1>3> 4th.
Furthermore, if there is an excessive difference in titanium concentration between toners, the density of an image formed with a toner having a relatively low titanium concentration may be reduced. Therefore, the titanium concentration ratio is set to the first toner: second toner: Third toner: Fourth toner = 1.6 to 1.9: 2.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1.

  In the toner set according to this embodiment, the titanium concentration ratio of each toner is as follows: first toner: second toner: third toner: fourth toner = 1.6 to 1.9: 2.0 to 2.4: 1. .2 to 1.5: 0.5 to 1.1, more preferably 1.7 to 1.8: 2.1 to 2.2: 1.3 to 1.4: 0.7 to 0 .9.

  The titanium concentration ratio between the first to fourth toners can be controlled by the amount of titanium oxide particles added externally to the toner particles constituting each of the four toners.

  Each toner in the toner set according to the present embodiment may contain an external additive other than the titanium oxide particles.

  In the toner set according to this embodiment, the color of each toner is not limited. In an embodiment of the toner set according to this embodiment, the first toner is yellow, the second toner is magenta, the third toner is cyan, and the fourth toner is black.

  Hereinafter, the material, composition, and manufacturing method of the toner in this embodiment will be described in detail.

[Toner particles]
The toner particles include, for example, a binder resin, a colorant, a release agent, and other additives.

  The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core / shell structure including a core (core particle) and a coating layer (shell layer) covering the core. Good. The toner particles having a core / shell structure include, for example, a core portion including a binder resin, a colorant, and a release agent, and a coating layer including the binder resin.

-Binder 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, acrylic acid). n-butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (for example, acrylonitrile, Methacrylonitrile, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (eg, vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene, Propylene, a homopolymer of a monomer such as butadiene) and the like, or a vinyl-based resin composed of these monomers with two or more combinations copolymer.
As the binder resin, for example, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, non-vinyl resin such as modified rosin, a mixture of these with the vinyl resin, or these Examples also include a graft polymer obtained by polymerizing a vinyl monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

  As the binder resin, a polyester resin is preferable from the viewpoint of image fixability, and a styrene- (meth) acrylate copolymer is preferable from the viewpoint of maintaining charge of the toner and weathering resistance of the image.

  Examples of the binder resin include modified polyester resins. The modified polyester resin is a polyester resin in which a bonding group other than an ester bond is present, and a polyester resin in which a resin different from the polyester resin is bonded by a covalent bond or an ionic bond. Examples of the modified polyester resin include a polyester resin having a terminal modified by reacting a polyester resin having a functional group such as an isocyanate group that reacts with an acid group or a hydroxyl group at the terminal and a compound having an active hydrogen group. It is done.

  As the modified polyester resin, a urea-modified polyester resin is preferable. The content of the urea-modified polyester resin is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 20% by mass or less with respect to the total binder resin.

  The urea-modified polyester resin is preferably a urea-modified polyester resin obtained by a reaction between a polyester resin having an isocyanate group (hereinafter referred to as “polyester prepolymer”) and an amine compound (at least one of a crosslinking reaction and an extension reaction). . In the urea-modified polyester, a urethane bond may exist together with a urea bond.

  Examples of the polyester prepolymer include a reaction product of a polyester having a group having active hydrogen and a polyvalent isocyanate compound. Examples of groups having active hydrogen include hydroxyl groups (alcoholic hydroxyl groups and phenolic hydroxyl groups), amino groups, carboxyl groups, mercapto groups, and the like, and alcoholic hydroxyl groups are preferred. Examples of the polyvalent isocyanate compound include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.); aromatic Diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanurates; polyisocyanates such as phenol derivatives, oximes, caprolactam Compound blocked with an agent: A polyvalent isocyanate compound may be used individually by 1 type, and may use 2 or more types together.

  The content of the site derived from the polyvalent isocyanate compound in the polyester prepolymer is preferably 0.5% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 30% by mass or less, based on the entire polyester prepolymer. 2 mass% or more and 20 mass% or less are still more preferable. The average number of isocyanate groups per molecule of the polyester prepolymer is preferably 1 or more, more preferably 1.5 to 3 and even more preferably 1.8 to 2.5.

  Examples of the amine compound that reacts with the polyester prepolymer include diamine, trivalent or higher polyamine, amino alcohol, amino mercaptan, amino acid, and compounds in which the amino group of these amine compounds is blocked.

Examples of the diamine include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′dimethyldicyclohexylmethane, diaminecyclohexane, isophoronediamine, etc. ); Aliphatic diamines (ethylenediamine, tetramethylenediamine, hexamethylenediamine, etc.); Examples of trivalent or higher polyamines include diethylenetriamine and triethylenetetramine. Examples of amino alcohols include ethanolamine and hydroxyethylaniline. Examples of amino mercaptans include aminoethyl mercaptan and aminopropyl mercaptan. Examples of amino acids include aminopropionic acid and aminocaproic acid.
Examples of the compound obtained by blocking the amino group of the amine compound include ketimine compounds and oxazoline compounds derived from the amine compounds and ketone compounds (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.).
As the amine compound, a ketimine compound is preferable. An amine compound may be used individually by 1 type, and may use 2 or more types together.

  The urea-modified polyester resin is a resin in which the molecular weight after the reaction is adjusted by adjusting the reaction between the polyester prepolymer and the amine compound with a stopper that stops at least one of the crosslinking reaction and the extension reaction. Good. Examples of the terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), compounds in which the amino group of monoamine is blocked (ketimine compounds), and the like.

The glass transition temperature (Tg) of the binder resin is preferably 50 ° C. or higher and 80 ° C. or lower, and more preferably 50 ° C. or higher and 65 ° C. or lower.
The glass transition temperature is obtained from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, it is described in “Supplement” described in the method for obtaining the glass transition temperature in JIS K7121-1987 “Method for measuring glass transition temperature”. It is determined by “outer glass transition start temperature”.

The weight average molecular weight (Mw) of the binder resin is preferably from 5,000 to 1,000,000, and more preferably from 7,000 to 500,000. The number average molecular weight (Mn) of the binder resin is preferably 2000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the binder resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.
The weight average molecular weight and number average molecular weight of the binder resin are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed with a tetrahydrofuran solvent using a Tosoh GPC / HLC-8120GPC as a measuring device and a Tosoh column / TSKgel SuperHM-M (15 cm). The weight average molecular weight and the number average molecular weight are calculated using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from this measurement result.

  The content of the binder resin is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and still more preferably 60% by mass to 85% by mass with respect to the entire toner particles.

-Colorant-
Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, and brilliant. Carmine 6B, Dupont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Pigments such as malachite green oxalate; acridine, xanthene, azo, benzox , Azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, and thiazole dyes It is done.
A coloring agent may be used individually by 1 type, and may use 2 or more types together.

  As the colorant, a surface-treated colorant may be used as necessary, or it may be used in combination with a dispersant. A plurality of colorants may be used in combination.

  The content of the colorant is 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 mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester types such as fatty acid esters and montanic acid esters Wax; and the like. The release agent is not limited to this.

  As the release agent, paraffin wax and olefin wax are preferable from the viewpoint of stabilizing toner charging because of a low content of impurities.

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) according to “melting peak temperature” described in JIS K7121: 1987 “Method for measuring melting temperature of plastic”.

  The content of the release agent is 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 known additives such as a magnetic material, a charge control agent, and inorganic powder. These additives are contained in the toner particles as internal additives.

-Toner particle characteristics-
The volume average particle diameter D50v of the toner particles is preferably 3 μm or more and 15 μm or less, more preferably 5 μm or more and 10 μm or less, and further preferably 5 μm or more and 8 μm or less.

  The volume particle size distribution index GSDv of the toner particles is preferably 1.00 or more and 1.50 or less, more preferably 1.00 or more and 1.40 or less, and further preferably 1.00 or more and 1.30 or less.

The volume average particle size D50v and the volume particle size distribution index GSDv of the toner particles are obtained by measuring the particle size distribution with a Coulter type particle size distribution measuring device (for example, Coulter Multisizer II manufactured by Beckman Coulter, Inc.). Specifically, the particle size distribution is measured according to the following procedure.
0.5 mg or more and 50 mg or less of toner is mixed with 2 ml of a 5% by weight aqueous solution of a surfactant (for example, sodium alkylbenzenesulfonate), and further, 100 ml or more and 150 ml or less of an electrolytic solution (for example, ISOTON-II manufactured by Beckman Coulter, Inc.). And dispersion treatment is performed for 1 minute with an ultrasonic disperser to prepare a dispersion. Using this dispersion as a measurement sample, the particle size of 50,000 particles having a particle size in the range of 2 μm to 60 μm is measured using a Coulter type particle size distribution measuring apparatus and an aperture having a diameter of 100 μm. A particle size distribution of 50,000 particles is drawn from the small diameter side on a volume basis, and a cumulative particle size of 16% is D16v, a cumulative particle size of 50% is a volume average particle size D50v, and a cumulative particle size of 84% is D84v. The volume particle size distribution index GSDv is (D84v ÷ D16v).

[External additive]
In the toner set according to this embodiment, each toner contains titanium oxide particles as an external additive. Examples of the titanium oxide include titanium oxide (TiO ₂ ) and metatitanic acid (TiO (OH) ₂ ). Metatitanic acid is preferable because it easily attenuates the charging of the toner because electrons easily move.

The volume average particle diameter of the titanium oxide particles is preferably 10 nm or more and 60 nm or less, more preferably 15 nm or more and 50 nm or less, and still more preferably 20 nm or more and 35 nm or less from the viewpoint of being hard to be embedded in the toner particles and difficult to be detached from the toner particles.
The volume average particle diameter of the titanium oxide particles is measured using a laser diffraction particle size distribution measuring apparatus (for example, Horiba LA-700).

In the toner set according to this embodiment, each toner may contain other external additives other than the titanium oxide particles. Other external additives include SiO 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. _{SiO 2, K 2 O · (} TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , etc. particles. Among these, silica particles (SiO ₂ ) and alumina particles (Al ₂ O ₃ ) are preferable.

The surface of the inorganic particles as an external additive is preferably subjected to a hydrophobic treatment. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used individually by 1 type and may use 2 or more types together.
The amount of the hydrophobizing agent is, for example, from 1 part by mass to 10 parts by mass with respect to 100 parts by mass of the inorganic particles.

  As external additives, resin particles (resin particles such as polystyrene, polymethyl methacrylate, melamine resin, etc.), cleaning activators (for example, metal salts of higher fatty acids represented by zinc stearate, particles of fluorine-based high molecular weight) And so on.

  The external addition amount of the external additive is 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.

  The ratio of the external addition amount of titanium oxide particles to the toner particles constituting each of the four toners of the toner set (mass basis) is as follows: first toner: second toner: third toner: fourth toner = 1.6 to 1. 9: 2.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1 are preferable, and 1.7 to 1.8: 2.1 to 2.2: 1.3 to 1. 4: 0.7 to 0.9 is more preferable.

[Toner Production Method]
The toner according to the exemplary embodiment can be obtained by externally adding an external additive to the toner particles after the toner particles are manufactured.

  The toner particles may be produced by any of a dry production method (for example, a kneading pulverization method) and a wet production method (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension method, an ester elongation method, etc.). There is no restriction | limiting in particular in these manufacturing methods, A well-known manufacturing method is employ | adopted. Among these, it is preferable to obtain toner particles by an aggregation and coalescence method.

Aggregation coalescence method When producing toner particles by the aggregation coalescence method, for example,
A step of preparing a resin particle dispersion in which resin particles to be a binder resin are dispersed (resin particle dispersion preparation step), and a resin particle dispersion (after mixing other particle dispersions as necessary) In the dispersion), agglomerating the resin particles (other particles as required) to form aggregated particles (aggregated particle forming step), and heating the aggregated particle dispersion in which the aggregated particles are dispersed to aggregate The toner particles are manufactured through a step of fusing and fusing the particles to form toner particles (fusing and fusing step).

Hereinafter, the detail of each process of the aggregation coalescence method is demonstrated.
In the following description, a method for obtaining toner particles containing a colorant and a release agent will be described. The colorant and the release agent are used as necessary. Of course, you may use other additives other than a coloring agent and a mold release agent.

-Preparation step of resin particle dispersion-
For example, a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared together with a resin particle dispersion in which resin particles serving as a binder resin are dispersed.

  The resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

Examples of the dispersion medium used for the resin particle dispersion include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together.

Examples of the surfactant include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap; cationic surfactants such as amine salt type and quaternary ammonium salt type; Nonionic surfactants such as polyethylene glycol, alkylphenol ethylene oxide adducts, and polyhydric alcohols can be used. Among these, anionic surfactants and cationic surfactants are particularly mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.
Surfactant may be used individually by 1 type and may use 2 or more types together.

  Examples of the method for dispersing the resin particles in the dispersion medium in the resin particle dispersion include a general dispersion method such as a rotary shear homogenizer, a ball mill having media, a sand mill, and a dyno mill. Depending on the type of resin particles, the resin particles may be dispersed in the dispersion medium by a phase inversion emulsification method. The phase inversion emulsification method is a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, neutralized by adding a base to the organic continuous phase (O phase), and then an aqueous medium (W phase). ) Is applied to perform phase inversion from W / O to O / W, and the resin is dispersed in the form of particles in the aqueous medium.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm to 1 μm, more preferably 0.08 μm to 0.8 μm, and further preferably 0.1 μm to 0.6 μm. preferable.
The volume average particle size of the resin particles is determined with respect to the volume of the divided particle size range (channel) using the particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring device (for example, LA-700 manufactured by Horiba, Ltd.). The cumulative distribution is subtracted from the small particle size side, and the particle size that is 50% cumulative with respect to all particles is measured as the volume average particle size D50v. The volume average particle size of the particles in the other dispersion is also measured in the same manner.

  5 mass% or more and 50 mass% or less are preferable, and, as for content of the resin particle contained in the resin particle dispersion liquid, 10 mass% or more and 40 mass% or less are more preferable.

  Similarly to the resin particle dispersion, a colorant particle dispersion and a release agent particle dispersion are also prepared. That is, the dispersion medium, the dispersion method, the volume average particle diameter of the particles, and the content of the particles in the resin particle dispersion are the same in the colorant particle dispersion and the release agent particle dispersion.

-Aggregated particle formation process-
Next, the resin particle dispersion, the colorant particle dispersion, and the release agent particle dispersion are mixed.
Then, in the mixed dispersion, resin particles, colorant particles, and release agent particles are hetero-aggregated to have resin particles, colorant particles, and release agent particles having a diameter close to the diameter of the target toner particles. Aggregated particles are formed.

Specifically, for example, a flocculant is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to acidic (for example, pH 2 to 5), and a dispersion stabilizer is added as necessary. To a temperature close to the glass transition temperature (specifically, for example, the glass transition temperature of the resin particles −30 ° C. or more and the glass transition temperature −10 ° C. or less), the particles dispersed in the mixed dispersion liquid are aggregated, Agglomerated particles are formed.
In the agglomerated particle forming step, for example, the agglomerated agent is added at room temperature (for example, 25 ° C.) while stirring the mixed dispersion with a rotary shearing homogenizer, and the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 to 5). In addition, heating may be performed after adding a dispersion stabilizer as necessary.

Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant contained in the mixed dispersion, an inorganic metal salt, and a bivalent or higher-valent metal complex. When a metal complex is used as the aggregating agent, the amount of the surfactant used is reduced and the charging characteristics are improved.
If necessary, an additive that forms a complex or a similar bond with the metal ion of the flocculant may be used together with the flocculant. As this additive, a chelating agent is preferably used.

Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; inorganic metal salts such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide Polymer; and the like.
A water-soluble chelating agent may be used as the chelating agent. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; aminocarboxylic acids such as iminodioic acid vinegar (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA); It is done.
The addition amount of the chelating agent is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of the resin particles.

-Fusion integration process-
Next, the agglomerated particle dispersion in which the agglomerated particles are dispersed is heated, for example, until the liquid temperature reaches the glass transition temperature or more of the resin particles, thereby fusing and aggregating the agglomerated particles.

Through the above steps, toner particles are obtained.
After obtaining the aggregated particle dispersion in which the aggregated particles are dispersed, the aggregated particle dispersion and the resin particle dispersion in which the resin particles are dispersed are further mixed, and the resin particles are further adhered to the surface of the aggregated particles. The second agglomerated particles are agglomerated to form a second agglomerated particle, and the second agglomerated particle dispersion is heated to fuse and coalesce the second agglomerated particles. The toner particles may be manufactured through a step of forming toner particles having a shell structure.

  After completion of the coalescence and coalescence process, the toner particles formed in the solution are subjected to a known washing process, solid-liquid separation process, and drying process to obtain dried toner particles. In the washing step, it is preferable to sufficiently perform substitution washing with ion exchange water from the viewpoint of chargeability. In the solid-liquid separation step, suction filtration, pressure filtration, or the like is preferably performed from the viewpoint of productivity. From the viewpoint of productivity, the drying step is preferably performed by freeze drying, air flow drying, fluidized drying, vibration fluidized drying, or the like.

Ester extension method The ester extension method is a method in which at least a polyester resin, a polymer having a site capable of reacting with a compound having an active hydrogen group, a colorant, and a release agent are dissolved or dispersed in an organic solvent, and then the dissolved product. Or it is the manufacturing method which disperse | distributes a dispersion in an aqueous medium and granulates.

  Examples of a method for producing toner particles containing a urea-modified polyester resin as a binder resin include an ester elongation method described below. In the following description, the ester elongation method will be described using toner particles containing a non-modified polyester resin and a urea-modified polyester resin as binder resins and also including a colorant and a release agent.

-Oil phase liquid preparation process-
An unmodified polyester resin, a polyester resin having an isocyanate group (referred to as “polyester prepolymer”), an amine compound, a colorant and a release agent are dissolved or dispersed in an organic solvent to prepare an oil phase liquid (oil phase liquid preparation step) ).

In the oil phase liquid preparation step, for example, any of the following operations is performed.
(I) All the toner materials are dissolved or dispersed in an organic solvent.
(Ii) After kneading all the toner materials in advance, the kneaded product is dissolved or dispersed in an organic solvent.
(Iii) An unmodified polyester resin, a polyester prepolymer, and an amine compound are dissolved in an organic solvent, and then a colorant and a release agent are dispersed.
(Iv) A colorant and a release agent are dispersed in an organic solvent, and then an unmodified polyester resin, a polyester prepolymer, and an amine compound are dissolved.
(V) Dissolve or disperse the unmodified polyester resin, the colorant and the release agent in the organic solvent, and then dissolve the polyester prepolymer and the amine compound.

  As the organic solvent of the oil phase liquid, an organic solvent in which the binder resin is dissolved and the amount dissolved in water is 0% by mass to 30% by mass and the boiling point is 100 ° C. or less is preferable. Examples of organic solvents for the oil phase liquid include ester solvents such as methyl acetate and ethyl acetate; ketone solvents such as methyl ethyl ketone and methyl isopropyl ketone; aliphatic hydrocarbon solvents such as hexane and cyclohexane; dichloromethane, chloroform, trichloroethylene, and the like Halogenated hydrocarbon solvents; and the like. Of these organic solvents, ethyl acetate is preferred.

-Dispersion preparation process-
An oil phase liquid is dispersed in an aqueous phase liquid to prepare a dispersion liquid (dispersion liquid preparation step).

  The aqueous phase liquid is an aqueous medium containing a dispersant. The aqueous medium contains water as a main component and may contain an organic solvent such as alcohol, dimethylformamide, tetrahydrofuran, cellosolves, and lower ketones. Dispersants include resin particles such as poly (meth) acrylic acid alkyl ester resins, polystyrene resins, poly (styrene-acrylonitrile) resins, polystyrene acrylic resins; silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate Inorganic particles such as clay, diatomaceous earth and bentonite. These particle dispersants may be surface-treated with a polymer having a carboxyl group on the surface. In addition, examples of the dispersant include polymer dispersants such as carboxymethyl cellulose and carboxyethyl cellulose.

  After preparing the dispersion, the polyester prepolymer is reacted with the amine compound. This reaction produces a urea-modified polyester resin. This reaction involves at least one of a molecular chain crosslinking reaction and an extension reaction. In addition, you may perform reaction of a polyester prepolymer and an amine compound in the organic solvent removal process mentioned later.

  For the reaction between the polyester prepolymer and the amine compound, a catalyst (dibutyltin laurate, dioctyltin laurate, etc.) may be used as necessary. That is, the catalyst may be added to the oil phase liquid or dispersion. The reaction time between the polyester prepolymer and the amine compound is preferably from 10 minutes to 40 hours, and more preferably from 2 hours to 24 hours. The reaction temperature is preferably 0 ° C. or higher and 150 ° C. or lower, and more preferably 40 ° C. or higher and 98 ° C. or lower.

-Solvent removal step-
An organic solvent is removed from the dispersion to form toner particles to obtain a toner particle dispersion (solvent removal step). In the solvent removal step, the organic solvent is removed from the dispersion by cooling or heating the dispersion in a range of, for example, 0 ° C. or more and 100 ° C. or less.

In the solvent removal step, for example, any one of the following operations is performed.
(I) A gas stream is sprayed on the dispersion to forcibly update the gas phase on the surface of the dispersion. When performing this operation, gas may be blown into the dispersion.
(Ii) Reduce the pressure around the dispersion. When performing this operation, the gas phase on the surface of the dispersion liquid may be forcibly updated by gas filling, or gas may be blown into the dispersion liquid.

  Through the above steps, toner particles are obtained. After completion of the solvent removal step, the toner particles formed in the solution are subjected to a known washing step, solid-liquid separation step, and drying step to obtain dried toner particles. In the washing step, it is preferable to sufficiently perform substitution washing with ion exchange water from the viewpoint of chargeability. In the solid-liquid separation step, suction filtration, pressure filtration, or the like is preferably performed from the viewpoint of productivity. From the viewpoint of productivity, the drying step is preferably performed by freeze drying, air flow drying, fluidized drying, vibration fluidized drying, or the like.

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

<Toner cartridge>
The toner cartridge contains replenishment toner to be supplied to the developing means provided in the image forming apparatus, and is attached to and detached from the image forming apparatus.

  The toner cartridge according to the present exemplary embodiment is a toner cartridge that accommodates the toner set according to the present exemplary embodiment and is detachable from the image forming apparatus. That is, the toner cartridge according to the present embodiment contains the first toner, the second toner, the third toner, and the fourth toner that contain toner particles and titanium oxide particles externally added to the toner particles as a set. The titanium concentration ratio of the first to fourth toners is such that the first toner: second toner: third toner: fourth toner = 1.6 to 1.9: 2.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1.

  In the toner cartridge according to the present embodiment, the preferred forms of the first to fourth toners are as described above.

<Static image developer set>
The electrostatic charge image developer set (hereinafter also referred to as “developer set”) according to the present embodiment includes a toner containing toner particles and titanium oxide particles externally added to the toner particles. Having a developer, a second developer, a third developer, and a fourth developer, the titanium concentration ratio of the toner contained in the first to fourth developers is the first developer: the second developer: the third development. Agent: Fourth developer = 1.6 to 1.9: 2.0 to 2.4: 1.2 to 1.5: 0.5 to 1.1.

  In the developer set according to this embodiment, the toner included in each of the first developer, the second developer, the third developer, and the fourth developer is the first toner, the second toner, and the third toner described above. And the fourth toner, and its preferred form is also as described above.

  In the developer set according to this embodiment, the color of each developer is not limited. In one embodiment of the developer set according to this embodiment, the first developer is yellow, the second developer is magenta, the third developer is cyan, and the fourth developer is black.

  In the developer set according to this embodiment, each developer may be a one-component developer containing only toner, or may be a two-component developer obtained by mixing toner and carrier.

  There is no restriction | limiting in particular as a carrier, A well-known carrier is mentioned. Examples of carriers include a coated carrier in which the surface of a core made of magnetic powder is coated with a resin; a magnetic powder-dispersed carrier in which magnetic powder is dispersed in a matrix resin; and a porous magnetic powder impregnated with resin. Resin impregnated type carriers; and the like. The magnetic powder-dispersed carrier and the resin-impregnated carrier may be a carrier whose constituent particles are used as a core and whose surface is coated with a resin.

  Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt; magnetic oxides such as ferrite and magnetite.

  Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene (meta). ) Acrylic ester copolymer, straight silicone resin comprising an organosiloxane bond or a modified product thereof, fluororesin, polyester, polycarbonate, phenol resin, epoxy resin and the like. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

In order to coat the surface of the core material with a resin, a method of coating with a coating layer forming solution in which a coating resin and various additives (used as necessary) are dissolved in an appropriate solvent may be mentioned. The solvent is not particularly limited, and may be selected in consideration of the type of resin used, application suitability, and the like.
Specific resin coating methods include a dipping method in which a core material is immersed in a coating layer forming solution; a spray method in which the coating layer forming solution is sprayed on the surface of the core material; A fluidized bed method in which a coating layer forming solution is sprayed; a kneader coater method in which a carrier core material and a coating layer forming solution are mixed in a kneader coater, and then the solvent is removed;

  As an embodiment of the carrier, a carrier obtained by coating magnetic particles having a volume average particle diameter of 10 μm or more and 60 μm or less (preferably 20 μm or more and 40 μm or less) with a resin can be given. As magnetic particles, ferrite particles are preferred.

  From the viewpoint of suppressing image density unevenness, the magnetic particles have a surface irregularity average spacing Sm of 1.0 μm ≦ Sm ≦ 3.5 μm and a surface arithmetic average roughness Ra of 0.2 μm ≦ Ra ≦ 0.7 μm. Preferably there is. When Sm and Ra are within this range, the contact frequency between the carrier and the toner is stabilized, the toner charge distribution is narrowed, and uneven image density is suppressed. From this viewpoint, it is more preferable that the magnetic particles have a surface irregularity average interval Sm of 2.0 μm ≦ Sm ≦ 3.0 μm and a surface arithmetic average roughness Ra of 0.4 μm ≦ Ra ≦ 0.5 μm. .

  The volume average particle diameter of the magnetic particles is measured using a laser diffraction particle size distribution measuring apparatus (for example, Horiba LA-700).

The average irregularity interval Sm and the arithmetic average roughness Ra of the surface of the magnetic particles are determined by observing the surface of 50 magnetic particles at a magnification of 3000 times using an ultra-deep color 3D shape measuring microscope (Keyence Corporation VK-9500).
The unevenness average interval Sm is an average value of intervals of one mountain and valley obtained by obtaining a roughness curve from the three-dimensional shape of the magnetic particle surface and obtaining from an intersection where the roughness curve intersects the average line. The reference length for determining the Sm value is 10 μm, and the cutoff value is 0.08 mm.
Arithmetic average roughness Ra is a value obtained by obtaining a roughness curve from the three-dimensional shape of the surface of the magnetic particles, and summing and averaging the measured value of the roughness curve and the absolute value of the deviation up to the average value. The reference length for determining the Ra value is 10 μm, and the cutoff value is 0.08 mm.
The Sm value and Ra value are measured according to JIS B0601: 1994.

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

<Image forming apparatus and image forming method>
The image forming apparatus according to the present embodiment includes four image carriers, two primary intermediate transfer members, and one secondary intermediate transfer member, and the electrostatic charge image developer set according to the present embodiment is applied thereto. The

That is, the image forming apparatus according to the present embodiment is
A first image carrier, a second image carrier, a third image carrier, a fourth image carrier,
First charging means for charging the surface of the first image carrier, second charging means for charging the surface of the second image carrier, third charging means for charging the surface of the third image carrier, and fourth A fourth charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged first image carrier, the charged second image carrier, the charged third image carrier, and the charged fourth image carrier;
First developing means for containing a first developer and developing the electrostatic image formed on the surface of the first image carrier as a toner image by the first developer;
Second developing means for containing a second developer and developing the electrostatic image formed on the surface of the second image carrier as a toner image with the second developer;
Third developing means for containing a third developer and developing the electrostatic image formed on the surface of the third image carrier as a toner image by the third developer;
Fourth developing means for containing a fourth developer, and developing the electrostatic image formed on the surface of the fourth image carrier as a toner image by the fourth developer;
A primary intermediate transfer body to which a toner image is transferred from a first image holding body and a second image holding body, and the second image holding body and the first image holding body from the upstream side in the rotation direction of the primary intermediate transfer body. A first intermediate transfer member in contact with these image carriers in order;
A primary intermediate transfer member to which a toner image is transferred from a third image carrier and a fourth image carrier, and the fourth image carrier and the third image carrier from the upstream side in the rotation direction of the primary intermediate transfer member. A second intermediate transfer member in contact with these image carriers in order;
A secondary intermediate transfer member to which a toner image is transferred from a first intermediate transfer member and a second intermediate transfer member, and the first intermediate transfer member and the second intermediate transfer member from the upstream side in the rotation direction of the secondary intermediate transfer member. A third intermediate transfer body in contact with these primary intermediate transfer bodies in the order of the body;
Transfer means for transferring the toner image transferred to the surface of the third intermediate transfer member to the surface of the recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
First cleaning means for cleaning toner remaining on the surface of the first image carrier after transferring the toner image;
A second cleaning means for cleaning toner remaining on the surface of the second image carrier after the toner image is transferred;
A third cleaning means for cleaning the toner remaining on the surface of the third image carrier after transferring the toner image;
A fourth cleaning means for cleaning the toner remaining on the surface of the fourth image carrier after transferring the toner image;
Is provided.

  The electrostatic image developer set according to this embodiment is applied to the image forming apparatus according to this embodiment.

  An example of an image forming apparatus according to the present embodiment will be described with reference to the drawings. In the following description, the first developing means forms a yellow (Y) toner image, the second developing means forms a magenta (M) toner image, and the third developing means cyan (C). In the embodiment, the toner image is formed and the fourth developing unit forms a black (K) toner image. However, the color of the toner image formed by each developing unit is not limited to this.

  FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus 10 which is an example of an image forming apparatus according to the present embodiment. The image forming apparatus 10 includes an image forming unit 20 in the center of the inside of the housing 12, an optical scanning device 50 on the right side of the image forming unit 20 in the drawing, and a recording medium before image recording below the image forming unit 20. A storage unit 14 for storing P is provided, and a conveyance path for the recording medium P is provided on the left side of the image forming unit 20 in the drawing.

  Above the storage unit 14, a take-out roll 16 for taking out the recording media P one by one from the storage unit 14, and an alignment roll 18 for adjusting the position of the leading end of the recording medium P taken out from the storage unit 14 by the take-out roll 16. Is provided.

  The optical scanning device 50 (an example of an electrostatic charge image forming unit) scans a light beam emitted from a light source with a rotating polygon mirror (polygon mirror), reflects the light beam with a plurality of optical components such as a reflection mirror, and the like. Beam 52Y, 52M, 52C or 52K is emitted. The light beams 52Y, 52M, 52C, and 52K are irradiated on the surfaces of the corresponding photoreceptors 22Y, 22M, 22C, and 22K, respectively, to form an electrostatic charge image on the surfaces.

  The image forming unit 20 includes a photoreceptor 22Y (an example of a first image carrier), a photoreceptor 22M (an example of a second image carrier), a photoreceptor 22C (an example of a third image carrier), and a photoreceptor 22K (a first image carrier). An example of a four-image holding member), and these four photoconductors are arranged in a line in the vertical direction.

  Around the photoreceptor 22Y, a charging roll 24Y (an example of a first charging unit) that charges the surface of the photoreceptor 22Y, and a developing device that develops the electrostatic image formed on the surface of the photoreceptor 22Y with yellow toner. 26Y (an example of a first developing unit) and a photoconductor cleaning device 28Y (an example of a first cleaning unit) that cleans the surface of the photoconductor 22Y before charging after transfer of a toner image are disposed.

  Around the photoreceptor 22M, a charging roll 24M (an example of a second charging unit) that charges the surface of the photoreceptor 22M, and a developing device that develops the electrostatic image formed on the surface of the photoreceptor 22M with magenta toner. 26M (an example of the second developing unit) and a photoconductor cleaning device 28M (an example of the second cleaning unit) that cleans the surface of the photoconductor 22M before charging after the transfer of the toner image are disposed.

  Around the photoreceptor 22C, a charging roll 24C (an example of a third charging unit) that charges the surface of the photoreceptor 22C, and a developing device that develops an electrostatic image formed on the surface of the photoreceptor 22C with cyan toner. 26C (an example of a third developing unit) and a photoconductor cleaning device 28C (an example of a third cleaning unit) that cleans the surface of the photoconductor 22C before charging after transfer of a toner image are disposed.

  Around the photosensitive member 22K, a charging roll 24K (an example of a fourth charging unit) that charges the surface of the photosensitive member 22K, and a developing device that develops an electrostatic image formed on the surface of the photosensitive member 22K with black toner. 26K (an example of a fourth developing unit) and a photoconductor cleaning device 28K (an example of a fourth cleaning unit) that cleans the surface of the photoconductor 22K before charging after transferring a toner image are disposed.

  In this embodiment, the titanium concentration ratio of toner contained in each developer contained in the developing devices 26Y, 26M, 26C, and 26K is 26Y: 26M: 26C: 26K = 1.6 to 1.9: 2.0. To 2.4: 1.2 to 1.5: 0.5 to 1.1.

  An intermediate transfer member 32 (an example of a first intermediate transfer member) is in contact with the photosensitive member 22Y and the photosensitive member 22M. The intermediate transfer body 32 is a primary intermediate transfer body to which a yellow toner image formed on the photoreceptor 22Y and a magenta toner image formed on the photoreceptor 22M are transferred. The intermediate transfer body 32 is in contact with the two photoconductors in the order of the photoconductor 22M and the photoconductor 22Y from the upstream side in the rotation direction (the arrow direction shown in the drawing).

  An intermediate transfer member 34 (an example of a second intermediate transfer member) is in contact with the photosensitive member 22C and the photosensitive member 22K. The intermediate transfer member 34 is a primary intermediate transfer member to which a cyan toner image formed on the photoconductor 22C and a black toner image formed on the photoconductor 22K are transferred. The intermediate transfer member 34 is in contact with the two photosensitive members in the order of the photosensitive member 22K and the photosensitive member 22C from the upstream side in the rotation direction (the arrow direction shown in the drawing).

  An intermediate transfer member 36 (an example of a third intermediate transfer member) is in contact with the intermediate transfer member 32 and the intermediate transfer member 34. The intermediate transfer member 36 is a secondary intermediate transfer member to which the toner image transferred to the intermediate transfer member 32 and the toner image transferred to the intermediate transfer member 34 are transferred. The intermediate transfer member 36 is in contact with the two primary intermediate transfer members in the order of the intermediate transfer member 32 and the intermediate transfer member 34 from the upstream side in the rotation direction (the arrow direction shown in the drawing).

  A transfer roll 38 (an example of a transfer unit) that transfers the toner image transferred to the intermediate transfer member 36 to the recording medium P is provided at a position facing the intermediate transfer member 36. The recording medium P is conveyed between the intermediate transfer body 36 and the transfer roll 38, and the toner image on the intermediate transfer body 36 is transferred to the recording medium P.

  A fixing device 60 (an example of a fixing unit) is provided downstream of the transfer roll 38 in the conveyance direction of the recording medium P. The fixing device 60 includes a heating belt 62 and a pressure roll 64, and heats and presses the recording medium P to fix the toner image on the recording medium P.

  A conveyance roll 66 is provided on the downstream side in the conveyance direction of the recording medium P with respect to the fixing device 60, and the recording medium P is discharged out of the apparatus by the conveyance roll 66 and stacked on the discharge unit 68.

  Next, the image forming operation of the image forming apparatus 10 will be described by taking a case where a full color image is formed as an example. In the following description, when it is necessary to distinguish YMCK, description is given by adding any of Y, M, C, and K after the reference numeral, and when it is not necessary to distinguish YMCK, YMCK is omitted.

  When the image forming apparatus 10 is operated, the surface of the photoreceptor 22 rotating in the direction of the arrow shown in the figure is charged by the charging roll 24.

  The light beam 52 of each color corresponding to the output image is irradiated from the optical scanning device 50 onto the surface of the photosensitive member 22 after charging, and an electrostatic charge image is formed on the surface of the photosensitive member 22.

  The developing device 26 applies toner to the electrostatic image on the surface of the photoreceptor 22, and a toner image is formed on the surface of the photoreceptor 22.

A magenta toner image is primarily transferred from the photoreceptor 22M to the intermediate transfer member 32, and then a yellow toner image is primarily transferred from the photoreceptor 22Y to the intermediate transfer member 32.
Similarly, a black toner image is primarily transferred from the photosensitive member 22K to the intermediate transfer member 34, and then a cyan toner image is primarily transferred from the photosensitive member 22C to the intermediate transfer member 34.

  After the toner image is transferred, the photoconductor 22 continues to rotate and comes into contact with a cleaning brush or a cleaning blade provided in the photoconductor cleaning device 28. The toner remaining on the photoconductor 22 is removed from the photoconductor 22 and collected by the photoconductor cleaning device 28.

  The magenta toner image and the yellow toner image on the intermediate transfer member 32 are secondarily transferred to the intermediate transfer member 36. Next, the black toner image and the cyan toner image on the intermediate transfer member 34 are also secondarily transferred to the intermediate transfer member 36.

  The four color toner images on the intermediate transfer body 36 reach the contact portion between the intermediate transfer body 36 and the transfer roll 38. In synchronization therewith, the recording medium P taken out from the storage unit 14 by the take-out roll 16 is transported to the contact part under the control of the alignment roll 18, and the four color toner images are transferred onto the recording medium P (final). Transferred).

  The recording medium P that has passed through the contact portion between the intermediate transfer body 36 and the transfer roll 38 is conveyed to the fixing device 60 and passes through the contact portion between the heating belt 62 and the pressure roll 64. At that time, the four color toner images are fixed on the recording medium P by the action of heat and pressure applied from the heating belt 62 and the pressure roll 64. After fixing, the recording medium P is discharged to the discharge unit 68 by the transport roll 66, and the image formation on the recording medium P is completed.

  The image forming apparatus according to the present exemplary embodiment includes a neutralizing unit that neutralizes the surface of the image holding member by irradiating the surface of the image holding member after the toner image is transferred and before charging; a cleaning unit that cleans the surface of the primary intermediate transfer member; A cleaning means for cleaning the surface of the intermediate transfer member may be provided.

  In the image forming apparatus according to the present embodiment, for example, the part including the developing unit may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail by way of examples, but the embodiments of the present invention are not limited to these examples. In the following description, all “parts” are based on mass unless otherwise specified.

[Production of Carrier (1)]
· _Fe 2 _O 3: 1318 parts · Mn (OH) _2: 586 parts · Mg (OH) _2: 96 parts of a mixture of the above materials, zirconia beads of water and diameter 1mm was added, mixed while pulverized in a sand mill did. Next, the zirconia beads were removed by filtration, dried, and then mixed for 60 minutes in a rotary kiln under the conditions of a rotation speed of 20 rpm and a temperature of 900 ° C. Next, polyvinyl alcohol and water were added, and the mixture was pulverized with a wet ball mill until the volume average particle size became 1.4 μm. Next, granulation and drying were performed using a spray dryer so that the dry particle size was 40 μm. Next, baking was performed in an electric furnace for 5 hours in an oxygen-nitrogen mixed atmosphere having a temperature of 1100 ° C. and an oxygen concentration of 1 vol%. The fired particles were crushed and classified, mixed for 2 hours in a rotary kiln under conditions of a rotation speed of 15 rpm and a temperature of 900 ° C., and classified after cooling to obtain magnetic particles (1). The magnetic particles (1) had a volume average particle size of 35 μm, a surface irregularity average spacing Sm of 2.5 μm, and a surface arithmetic average roughness Ra of 0.4 μm.

-Cyclohexyl methacrylate-monoethylaminoethyl methacrylate copolymer (mass ratio 95: 5, weight average molecular weight 60,000): 36 parts-Carbon black (Cabot, VXC72): 4 parts-Toluene (Wako Pure Chemical Industries): 500 Parts / Isopropyl alcohol (Wako Pure Chemical Industries): 50 parts The above materials and glass beads of the same amount as toluene (particle size: 1 mm) are placed in a sand mill and stirred for 30 minutes at 1200 rpm for coating layer formation. Solution (1) was prepared.

  200 parts of the magnetic particles (1) and 34 parts of the coating layer forming solution (1) were put into a vacuum degassing kneader, and the pressure was reduced to −200 mmHg at 60 ° C. with stirring, and mixed for 20 minutes. Next, the temperature was increased and the pressure was reduced, and the mixture was stirred and dried at 94 ° C. and −720 mmHg for 30 minutes to obtain resin-coated magnetic particles. The resin-coated magnetic particles were sieved with a 75 μm mesh sieve to obtain carrier (1).

[Preparation of Colorant Dispersion (Y)]
・ Pigment: Pigment Yellow 74 (Daiichi Seika Kogyo): 50 parts ・ Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts ・ Ion-exchanged water: 200 parts The above materials were mixed and homogenizer (IKA) Dispersion treatment was carried out for 5 minutes using an Ultra Turrax T50), and further dispersion treatment was carried out for 10 minutes using an ultrasonic bath to obtain a colorant dispersion (Y) having a solid content of 21% by mass. It was 160 nm when the volume average particle diameter was measured with a particle size distribution measuring apparatus (LA-700 manufactured by Horiba Seisakusho).

[Preparation of Colorant Dispersion (M)]
Pigment: Pigment Red 122 (DIC): 50 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts Ion-exchanged water: 200 parts Same as the preparation of the colorant dispersion (Y) Thus, a colorant dispersion (M) having a solid content of 21% by mass and a volume average particle size of 160 nm was obtained.

[Preparation of Colorant Dispersion (C)]
・ Pigment: Pigment Blue 15: 3 (Daisen Seika Kogyo): 50 parts ・ Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts ・ Ion-exchanged water: 200 parts Colorant dispersion (Y) In the same manner as in the preparation, a colorant dispersion (C) having a solid content of 21% by mass and a volume average particle size of 160 nm was obtained.

[Preparation of Colorant Dispersion (K)]
Pigment: Carbon black (Cabot, Regal 330): 50 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 5 parts Ion-exchanged water: 200 parts Preparation of colorant dispersion (Y) Similarly, a colorant dispersion (K) having a solid content of 21% by mass and a volume average particle size of 160 nm was obtained.

[Preparation of release agent dispersion (1)]
-Paraffin wax: HNP-9 (Nippon Seiwa): 19 parts-Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 1 part-Ion-exchanged water: 80 parts The above materials are mixed in a heat-resistant container. The mixture was 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 after a circulation operation corresponding to 3 passes under a pressure of 5 MPa, the pressure was increased to 35 MPa, and a circulation operation corresponding to 3 passes was further performed. The emulsion thus prepared was cooled in a heat resistant solution to 40 ° C. or lower to obtain a release agent dispersion (1) having a solid content of 20% by mass. It was 240 nm when the volume average particle diameter was measured with a particle size distribution analyzer (LA-700 manufactured by Horiba, Ltd.).

[Preparation of resin particle dispersion (1)]
-Oil phase material-
• Styrene (Wako Pure Chemical Industries): 30 parts • N-butyl acrylate (Wako Pure Chemical Industries): 10 parts • β-carboxyethyl acrylate (Rhodia Nikka): 1.3 parts • Dodecanethiol (Wako Pure Chemical Industries) : 0.4 part

-Material of aqueous phase 1-
・ Ion-exchanged water: 17 parts ・ Anionic surfactant: Dowfax (Dow Chemical): 0.4 parts

-Material of aqueous phase 2-
・ Ion-exchanged water: 40 parts ・ Anionic surfactant: Dowfax (Dow Chemical): 0.05 part ・ Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries): 0.4 part

The material of the oil phase and the material of the aqueous phase 1 were respectively stirred and mixed, and both were stirred and mixed to obtain an emulsified dispersion of monomers. Separately, the material of the aqueous phase 2 was charged into the reaction vessel, the inside of the reaction vessel was sufficiently replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The emulsion dispersion of the monomer was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours to obtain a resin particle dispersion (1) having a solid content of 42% by mass.
It was 250 nm when the volume average particle diameter was measured with a particle size distribution analyzer (LA-700 manufactured by Horiba, Ltd.). It was 52 degreeC when the glass transition temperature of resin was measured with the temperature increase rate of 10 degree-C / min with the differential scanning calorimeter (Shimadzu DSC-50). It was 13000 when the number average molecular weight (polystyrene conversion) was measured by GPC.

[Production of Toner Particles (Y1)]
-Resin particle dispersion (1): 150 parts-Colorant dispersion (Y): 25 parts-Release agent dispersion (1): 35 parts-Polyaluminum chloride: 0.4 parts After mixing and dispersing in a flask made using a homogenizer (Ultra Turrax T50 manufactured by IKA), the flask was heated to 48 ° C. with a heating oil bath while stirring. After holding at 48 ° C. for 60 minutes with stirring, 70 parts of the resin particle dispersion (1) was slowly added. Next, after adjusting the pH in the system to 8.0 using a sodium hydroxide aqueous solution having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heated to 90 ° C. and held at that temperature for 30 minutes. Subsequently, the mixture was cooled at a cooling rate of 5 ° C./min, filtered, and the solid content was sufficiently washed with ion-exchanged water, followed by solid-liquid separation by Nutsche suction filtration. The solid content was redispersed in 3 L of ion-exchanged water at 30 ° C., and the mixture was stirred and washed at a rotation speed of 300 rpm for 15 minutes. This washing operation was further repeated 6 times, and when the pH of the filtrate became 7.54 and the electric conductivity was 6.5 μS / cm, No. was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. The solid content was vacuum dried for 24 hours to obtain toner particles (Y1). The volume average particle diameter was measured and found to be 5.7 μm.

[Production of Toner Particles (M1)]
Toner particles (M1) were prepared in the same manner as the toner particles (Y1) except that the colorant dispersion (Y) was changed to the colorant dispersion (M). The volume average particle diameter was measured and found to be 5.7 μm.

[Production of Toner Particles (C1)]
Toner particles (C1) were prepared in the same manner as the toner particles (Y1) except that the colorant dispersion (Y) was changed to the colorant dispersion (C). The volume average particle diameter was measured and found to be 5.7 μm.

[Production of Toner Particles (K1)]
Toner particles (K1) were prepared in the same manner as the toner particles (Y1) except that the colorant dispersion (Y) was changed to the colorant dispersion (K). The volume average particle diameter was measured and found to be 5.7 μm.

[Preparation of hydrophobic titanium oxide particles (1)]
Ilmenite ore (FeTiO ₃ ) was heated and dissolved in concentrated sulfuric acid, and iron powder was separated to obtain titanium oxysulfate (TiOSO ₄ ). Next, titanium oxysulfate is hydrolyzed by heating to produce a metatitanic acid (TiO (OH) ₂ ) precipitate, the precipitate is filtered, washed repeatedly with water, and then 10 ppm (mass basis) with respect to metatitanic acid. The polycarboxylic acid and 100 times the amount (by mass) of water were added and stirred sufficiently, followed by drying at 150 ° C. Then, 500 ° C., subjected to heating and baking in a 100 minute conditions to obtain titanium oxide (TiO ₂₎ and metatitanic acid (TiO _{(OH) 2)} and titanium oxide containing (1). Next, the titanium oxide (1) was dispersed in water, and 5% by mass of isobutylmethoxysilane was added dropwise to the titanium oxide (1) at a liquid temperature of 25 ° C. while stirring the dispersion. Subsequently, the solid and liquid were separated by filtration, and after washing the solid content with water repeatedly, the solid content was dried at 150 ° C. Next, the dried product was redispersed in 100 times (mass basis) of methanol, solid-liquid separated by filtration, and dried at 100 ° C. Thus, hydrophobic titanium oxide particles (1) obtained by surface-treating titanium oxide (1) with isobutylmethoxysilane were obtained. When the volume average particle size was measured with a particle size distribution analyzer (LA-700 manufactured by Horiba, Ltd.), the volume average particle size of the hydrophobic titanium oxide particles (1) was 50 nm.

<Example 1>
[Preparation of external toner]
To 500 parts of toner particles (Y1), 10 parts of silica particles (Japan Aerosil, RY50, volume average particle size 40 nm) and 8.5 parts of titanium oxide particles (Taika, JMT2000, volume average particle size 20 nm) are added. And an Henschel mixer to obtain an externally added toner (Y1).
To 500 parts of the toner particles (M1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 11 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (M1). Obtained.
To 500 parts of the toner particles (C1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 7 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (C1). Obtained.
To 500 parts of the toner particles (K1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 4 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (K1). Obtained.

[Production of developer]
10 parts of each externally added toner and 100 parts of carrier (1) are put in a V blender, stirred for 20 minutes and mixed, and then sieved with a sieve having a mesh opening of 212 μm to develop the developer (Y1), (M1), ( A set of C1) and (K1) was obtained.
The toner was separated from each developer, and the titanium concentration ratio between the toners was calculated according to the measurement method described above. Table 2 shows the titanium concentration ratio.

[Evaluation of density unevenness]
As an image forming apparatus having the configuration illustrated in FIG. 1, DocuPrint C3200A manufactured by Fuji Xerox was prepared. Developers (Y1), (M1), (C1) and (K1) are placed in each of the four developing devices of this image forming apparatus, and the density is applied to A4 plain paper in an environment of a temperature of 10 ° C. and a relative humidity of 10%. A total of 10,000 sheets of 30% full-screen halftone images were continuously output in the order of yellow single color, magenta single color, cyan single color, and black single color. (1) The 4999th cyan monochrome full-color halftone image and (2) 9999 cyan monochrome full-color halftone image were visually observed and classified as follows. Table 2 shows the results.

G1: No density unevenness is observed in both (1) and (2).
G2: Density unevenness is not recognized in (1), but a slight streaky density unevenness is observed in (2).
G3: Density unevenness is not recognized in (1), but a low density portion is widely observed in a band shape in (2).
G4: Streaky density unevenness is observed in (1).
G5: A white stripe-like image is observed in (1).

  After a total of 10,000 sheets were output continuously, the surface of the third photoreceptor, which is a photoreceptor using a cyan developer, was visually observed, and the presence or absence of toner filming was classified as follows. Table 2 shows the results.

A: Toner filming is not recognized.
B: Minute toner filming is observed.
C: A lot of toner filming or a wide area occurs.

[Evaluation of concentration reduction]
The A4 plain paper, to form a reference patch of 100% density using an external addition toner ^{(C1), CIE1976L * a *} b * L * values in a color system, the ^{a *} and ^{b *} values, X-Rite It measured using X-Rite939 (aperture diameter 4mm) made from.
After 10,000 sheets of continuous output performed for [Evaluation of density unevenness], one 100% cyan density image is output, and the L ^* value, a ^* value, and b ^* value are set in the same manner as described above. It was measured.
Based on the following equation, the color difference ΔE between the reference patch and the image formed with the actual machine was calculated between cyan colors.

L ₁ , a ₁ , and b ₁ are the L ^* value, a ^* value, and b ^* value of the reference patch, and L ₂ , a ₂ , and b ₂ are the L ^* value and a ^* value of the image formed with the actual machine. , B ^* value.

  The value of the color difference ΔE between the reference patch and the image formed with the actual machine was classified as follows. Table 2 shows the results.

G1: ΔE is 1.0 or less.
G2: ΔE is more than 1.0 and not more than 2.0.
G3: ΔE is more than 2.0 and 3.0 or less.
G4: ΔE is more than 3.0 and 4.0 or less.
G5: ΔE is over 4.0.

[Evaluation of fogging]
Developers (Y1), (M1), (C1) and (K1) are placed in each of the four development devices of Fuji Xerox DocuPrint C3200A, and full color is printed on A4 plain paper in an environment of a temperature of 25 ° C. and a relative humidity of 80%. 50,000 test charts were continuously output, and the last 10 sheets were visually observed and classified as follows. Table 2 shows the results.

G1: No fogging is observed on all 10 sheets.
G2: Slight fogging is observed on one sheet, but this is a practically acceptable range.
G3: Slight fogging is observed on a plurality of sheets, but this is a practically acceptable range.
G4: Obvious fogging is recognized on a plurality of sheets, which is not suitable for practical use.
G5: All 10 sheets are completely covered with fog.

<Examples 2-12, Comparative Examples 1-10>
A toner set and a developer set were produced in the same manner as in Example 1 except that the addition amount of titanium oxide particles (Taika, JMT2000) was changed as shown in Table 1. The toner was separated from each developer, and the titanium concentration ratio between the toners was calculated according to the measurement method described above. Table 2 shows the titanium concentration ratio.
Then, using each developer set, an image was formed and evaluated in the same manner as in Example 1. Table 2 shows the results.
The tin oxide particles used in Comparative Example 9 are SnO ₂ (Ishihara Sangyo Co., Ltd., SN-100P, volume average particle size 20 nm).

<Example 13>
[Preparation of polyester particle dispersion (1)]
・ Terephthalic acid: 30 mol parts ・ Fumaric acid: 70 mol parts ・ Bisphenol A ethylene oxide adduct: 5 mol parts ・ Bisphenol A propylene oxide adduct: 95 mol parts A stirrer, nitrogen introduction tube, temperature sensor and rectifying tower The above-mentioned material was charged into the flask equipped, and the temperature was raised to 220 ° C. over 1 hour, and 1 part of titanium tetraethoxide was added to 100 parts of the material. The temperature was raised to 230 ° C. over 0.5 hours while distilling off the produced water, and the dehydration condensation reaction was continued at that temperature for 1 hour, and then the reaction product was cooled. Thus, a polyester resin having a weight average molecular weight of 18000, an acid value of 15 mgKOH / g, and a glass transition temperature of 60 ° C. was obtained.

In a container equipped with a temperature control means and a nitrogen substitution means, 40 parts of ethyl acetate and 25 parts of 2-butanol were mixed to form a mixed solvent, and then 100 parts of a polyester resin was gradually added and dissolved therein. % Aqueous ammonia solution (corresponding to 3 times the molar ratio with respect to the acid value of the resin) was added and stirred for 30 minutes.
Next, the inside of the container was replaced with dry nitrogen, the temperature was kept at 40 ° C., and 400 parts of ion-exchanged water was added dropwise at a rate of 2 parts / minute while stirring the mixed solution to carry out emulsification. After completion of the dropwise addition, the emulsion was returned to room temperature (20 ° C. to 25 ° C.) and bubbled with dry nitrogen for 48 hours while stirring to reduce ethyl acetate and 2-butanol to 0.1% by mass or less. Thereafter, ion-exchanged water was added to adjust the solid content to 20% by mass to obtain a polyester particle dispersion (1). The volume average particle size of the resin particles in the dispersion was 200 nm.

[Production of Toner Particles (YP1)]
Polyester particle dispersion (1): 150 parts Colorant dispersion (Y): 30 parts Release agent dispersion (1): 40 parts Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku): 1 part Said material was put into the reaction container provided with the thermometer, the pH meter, and the stirrer, it heated from the outside to the temperature of 30 degreeC with the mantle heater, and it hold | maintained for 30 minutes, stirring at 150 rpm. Subsequently, after adding 0.3N nitric acid aqueous solution and adjusting pH to 3.0, 3 mass% poly aluminum chloride aqueous solution was added, disperse | distributing with a homogenizer (Ultra Tarax T50 by IKA). Subsequently, it heated up to 50 degreeC, stirring, and hold | maintained for 30 minutes. Next, 100 parts of the polyester particle dispersion (1) was added and held for 1 hour. After adjusting the pH to 8.5 by adding a 0.1N sodium hydroxide aqueous solution, the mixture was heated to 85 ° C. while stirring was continued. And held at the temperature for 5 hours. Subsequently, cooling, solid-liquid separation, washing of solids and drying were sequentially performed to obtain toner particles (YP1). The volume average particle size of the toner particles (YP1) was 6.2 μm.

[Production of Toner Particles (MP1)]
Toner particles (MP1) were prepared in the same manner as the toner particles (YP1) except that the colorant dispersion (Y) was changed to the colorant dispersion (M). The volume average particle diameter of the toner particles (MP1) was 6.2 μm.

[Production of Toner Particles (CP1)]
Toner particles (CP1) were prepared in the same manner as the toner particles (YP1) except that the colorant dispersion (Y) was changed to the colorant dispersion (C). The volume average particle size of the toner particles (CP1) was 6.2 μm.

[Production of Toner Particles (KP1)]
Toner particles (KP1) were prepared in the same manner as the toner particles (YP1) except that the colorant dispersion (Y) was changed to the colorant dispersion (K). The volume average particle diameter of the toner particles (KP1) was 6.2 μm.

[Preparation of external toner]
To 500 parts of toner particles (YP1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 8.5 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer, and externally added toner (YP1). )
To 500 parts of toner particles (MP1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 11 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add externally added toner (MP1). Obtained.
To 500 parts of toner particles (CP1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 7 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add externally added toner (CP1). Obtained.
To 500 parts of toner particles (KP1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 4 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add externally added toner (KP1). Obtained.

[Production of developer]
10 parts of each externally added toner and 100 parts of carrier (1) are put into a V blender, stirred for 20 minutes and mixed, and then sieved with a sieve having an opening of 212 μm to develop the developer (YP1), (MP1), ( A set of CP1) and (KP1) was obtained.
When the toner was separated from each developer and the titanium concentration ratio between the toners was calculated according to the measurement method described above, the toner (YP1): toner (MP1): toner (CP1): toner (KP1) = 1.7: 2.2: 1.4: 0.8.

[Image formation and image evaluation]
The developer set was placed in each of four development apparatuses of DocuPrint C3200A manufactured by Fuji Xerox, and image formation was performed in the same manner as in Example 1 to evaluate density unevenness, density reduction, and fogging. The density unevenness was G1, the density reduction was G1, and the fog was G1.

<Example 14>
[Preparation of Unmodified Polyester Resin (A)]
-Terephthalic acid: 1243 parts-Bisphenol A ethylene oxide adduct: 1830 parts-Bisphenol A propylene oxide adduct: 840 parts After mixing the above materials while heating at 180 ° C, add 3 parts of dibutyltin oxide, and at 220 ° C Water was distilled off while heating to obtain an unmodified polyester resin (A). The glass transition temperature Tg of the unmodified polyester resin (A) was 60 ° C.

[Preparation of polyester prepolymer (A)]
-Terephthalic acid: 1243 parts-Bisphenol A ethylene oxide adduct: 1830 parts-Bisphenol A propylene oxide adduct: 840 parts After mixing the above materials while heating at 180 ° C, add 3 parts of dibutyltin oxide, and at 220 ° C Water was distilled off while heating to obtain a polyester resin. 350 parts of the polyester resin, 50 parts of tolylene diisocyanate, and 450 parts of ethyl acetate were mixed in a container and heated at 130 ° C. for 3 hours to obtain a polyester prepolymer (A) having an isocyanate group.

[Preparation of ketimine compound (A)]
A container was charged with 50 parts of methyl ethyl ketone and 150 parts of hexamethylenediamine, and stirred at 60 ° C. to obtain a ketimine compound (A).

[Preparation of Colorant Dispersion (YA)]
Pigment: Pigment Yellow 74 (Daiichi Seika Kogyo): 30 parts Ethyl acetate: 270 parts The above materials are wet-ground by a microbead type disperser (DCP mill), and a colorant dispersion (YA) having a solid content of 10% by mass )

[Preparation of Colorant Dispersion (MA)]
Pigment: Pigment Red 122 (DIC Corporation): 30 parts Ethyl acetate: 270 parts The above material is wet-ground by a microbead type disperser (DCP mill), and a solid content 10% by mass of a colorant dispersion (MA) is obtained. Obtained.

[Preparation of Colorant Dispersion (CA)]
Pigment Blue 15: 3 (Daiichi Seika Kogyo): 30 parts Ethyl acetate: 270 parts The above materials are wet-ground by a microbead disperser (DCP mill), and a colorant dispersion having a solid content of 10% by mass (CA) was obtained.

[Preparation of Colorant Dispersion (KA)]
Pigment: Carbon black (Cabot, Regal 330): 30 parts Ethyl acetate: 270 parts The above materials are wet-ground with a microbead type disperser (DCP mill), and a solid colorant dispersion (KA) (KA) )

[Preparation of Release Agent Dispersion (A)]
-Paraffin wax: HNP-9 (Nippon Seiwa): 30 parts-Ethyl acetate: 270 parts In the state where the above materials are cooled to 10 ° C, they are wet-ground by a microbead disperser (DCP mill), and the solid content is 10 mass. % Release agent dispersion (A).

[Preparation of styrene acrylic resin particle dispersion (A)]
-Styrene: 332 parts-n-butyl acrylate: 68 parts-Acrylic acid: 4 parts-Dodecanethiol: 8 parts-Carbon tetrabromide: 4 parts Nonionic surfactant (Nonipol 400, Sanyo Chemical Industries) in the flask ) A solution prepared by dissolving 6 parts and 10 parts of an anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku Co., Ltd.) in 560 parts of ion-exchanged water was prepared. did. Next, while stirring the inside of the flask, a solution in which 4 parts of ammonium persulfate was dissolved in 50 parts of ion-exchanged water was added to perform nitrogen substitution. Next, while stirring the inside of the flask, the contents were heated in an oil bath until the content reached 70 ° C., and emulsion polymerization was continued for 5 hours. The styrene acrylic resin particle dispersion (A) (resin particle volume average particle diameter 180 nm, solid 40 mass%) was obtained. The styrene acrylic resin had a glass transition temperature of 59 ° C. and a weight average molecular weight of 15500.

[Preparation of oil phase liquid (A)]
Unmodified polyester resin (A): 60 parts Colorant dispersion (YA): 50 parts Release agent dispersion (A): 70 parts Ethyl acetate: 30 parts Ethyl acetate, unmodified polyester resin (A) The colorant dispersion (YA) was stirred and mixed, and then the release agent dispersion (A) was added to the mixture and further stirred to obtain an oil phase liquid (A).

[Preparation of aqueous phase liquid (A)]
-Styrene acrylic resin particle dispersion (A): 50 parts-Polymer dispersant (2% by weight aqueous solution of Serogen BS-H (Daiichi Kogyo Seiyaku)): 200 parts-Ion-exchanged water: 200 parts To obtain an aqueous phase liquid (A).

[Production of Toner Particles (YA1)]
Oil phase liquid (A): 1200 parts Polyester prepolymer (A): 150 parts Ketimine compound (A): 10 parts The above materials are put in a container and dispersed for 2 minutes with a homogenizer (Ultra Turrax T50 manufactured by IKA). Treatment was performed to obtain an oil phase liquid (AP). 1000 parts of the aqueous phase liquid (A) was added to the oil phase liquid (AP), and dispersion treatment was performed with a homogenizer for 20 minutes to obtain a dispersion liquid. Next, the dispersion is stirred with a propeller-type stirrer at room temperature (25 ° C.) and normal pressure (1 atm) for 48 hours to react the polyester prepolymer (A) with the ketimine compound (A), and a urea-modified polyester resin And the organic solvent was removed to form a granular material. Next, the granular material was washed with water, dried and classified to obtain toner particles (YA1). The volume average particle diameter of the toner particles (YA1) was 6.0 μm.

[Production of Toner Particles (MA1)]
Toner particles (MA1) were prepared in the same manner as the toner particles (YA1) except that the colorant dispersion (YA) was changed to the colorant dispersion (MA). The volume average particle size of the toner particles (MA1) was 6.0 μm.

[Production of Toner Particles (CA1)]
Toner particles (CA1) were prepared in the same manner as the toner particles (YA1) except that the colorant dispersion (YA) was changed to the colorant dispersion (CA). The volume average particle size of the toner particles (CA1) was 6.0 μm.

[Production of Toner Particles (KA1)]
Toner particles (KA1) were prepared in the same manner as the toner particles (YA1) except that the colorant dispersion (YA) was changed to the colorant dispersion (KA). The volume average particle size of the toner particles (KA1) was 6.0 μm.

[Preparation of external toner]
To 500 parts of toner particles (YA1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 8.5 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer, and externally added toner (YA1). )
To 500 parts of toner particles (MA1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 11 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (MA1). Obtained.
To 500 parts of the toner particles (CA1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 7 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (CA1). Obtained.
To 500 parts of the toner particles (KA1), 10 parts of silica particles (Nippon Aerosil Co., Ltd., RY50) and 4 parts of titanium oxide particles (Taika Co., Ltd., JMT2000) are added and mixed with a Henschel mixer to add the externally added toner (KA1). Obtained.

[Production of developer]
10 parts of each externally added toner and 100 parts of carrier (1) are placed in a V blender, stirred and mixed for 20 minutes, and then sieved with a sieve having an opening of 212 μm to develop the developer (YA1), (MA1), ( A set of CA1) and (KA1) was obtained.
The toner was separated from each developer, and the titanium concentration ratio between the toners was calculated according to the measurement method described above. As a result, toner (YA1): toner (MA1): toner (CA1): toner (KA1) = 1.7: 2.2: 1.4: 0.8.

[Image formation and image evaluation]
The developer set was placed in each of four development apparatuses of DocuPrint C3200A manufactured by Fuji Xerox, and image formation was performed in the same manner as in Example 1 to evaluate density unevenness, density reduction, and fogging. The density unevenness was G1, the density reduction was G1, and the fog was G1.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Case 14 Housing | casing part 16 Take-out roll 18 Positioning roll 20 Image forming unit 22Y Photosensitive body (an example of a 1st image holding body)
22M photoconductor (an example of a second image carrier)
22C photoconductor (an example of a third image carrier)
22K photoconductor (an example of a fourth image carrier)
24Y charging roll (an example of first charging means)
24M charging roll (an example of second charging means)
24C charging roll (an example of third charging means)
24K charging roll (an example of fourth charging means)
26Y developing device (an example of first developing means)
26M developing device (example of second developing means)
26C developing device (example of third developing means)
26K developing device (example of fourth developing means)
28Y Photoconductor cleaning device (an example of first cleaning means)
28M photoconductor cleaning device (an example of second cleaning means)
28C photoreceptor cleaning device (an example of third cleaning means)
28K photoconductor cleaning device (an example of fourth cleaning means)
32 Intermediate transfer member (an example of a first intermediate transfer member)
34 Intermediate transfer member (an example of a second intermediate transfer member)
36 Intermediate transfer member (an example of a third intermediate transfer member)
38 Transfer roll (an example of transfer means)
50 Optical scanning device (an example of electrostatic charge image forming means)
52Y, 52M, 52C, 52K Light beam 60 Fixing device (an example of fixing means)
62 Heating belt 64 Pressure roll 66 Conveying roll 68 Discharge part P Recording medium

Claims (7)

A first toner, a second toner, a third toner, and a fourth toner containing toner particles and titanium oxide particles externally added to the toner particles;
The titanium concentration ratio of the first to fourth toners is as follows: first toner: second toner: third toner: fourth toner = 1.6 to 1.9: 2.0 to 2.4: 1.2 to 1. .5: Toner set for developing an electrostatic charge image of 0.5 to 1.1.   The toner set for developing electrostatic images according to claim 1, wherein the titanium oxide particles are particles containing at least one of titanium oxide and metatitanic acid. Containing the toner set for developing an electrostatic charge image according to claim 1,
A toner cartridge to be attached to and detached from the image forming apparatus. A first developer, a second developer, a third developer, and a fourth developer, including toner containing toner particles and titanium oxide particles externally added to the toner particles;
The titanium concentration ratio of the toner contained in the first to fourth developers is as follows: first developer: second developer: third developer: fourth developer = 1.6 to 1.9: 2.0 to 2.4: The electrostatic charge image developer set which is 1.2 to 1.5: 0.5 to 1.1.   The electrostatic charge image developer set according to claim 4, wherein the titanium oxide particles are particles containing at least one of titanium oxide and metatitanic acid. A first image carrier, a second image carrier, a third image carrier, a fourth image carrier,
First charging means for charging the surface of the first image carrier, second charging means for charging the surface of the second image carrier, and third charging means for charging the surface of the third image carrier. A fourth charging means for charging the surface of the fourth image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged first image carrier, the charged second image carrier, the charged third image carrier, and the charged fourth image carrier. When,
First developing means for containing a first developer and developing the electrostatic image formed on the surface of the first image carrier as a toner image by the first developer;
Second developing means for containing a second developer and developing the electrostatic image formed on the surface of the second image carrier as a toner image by the second developer;
Third developing means for containing a third developer and developing an electrostatic charge image formed on the surface of the third image carrier as a toner image by the third developer;
Fourth developing means for containing a fourth developer, and developing the electrostatic image formed on the surface of the fourth image carrier as a toner image by the fourth developer;
A primary intermediate transfer body to which a toner image is transferred from the first image holding body and the second image holding body, wherein the second image holding body and the first image transfer body from the upstream side in the rotation direction of the primary intermediate transfer body. A first intermediate transfer member in contact with these image carriers in the order of the image carrier;
A primary intermediate transfer body to which a toner image is transferred from the third image holding body and the fourth image holding body, wherein the fourth image holding body and the third image transfer body from the upstream side in the rotation direction of the primary intermediate transfer body; A second intermediate transfer member in contact with these image carriers in the order of the image carriers;
A secondary intermediate transfer body to which a toner image is transferred from the first intermediate transfer body and the second intermediate transfer body, the first intermediate transfer body from the upstream side in the rotation direction of the secondary intermediate transfer body; A third intermediate transfer member in contact with these primary intermediate transfer members in the order of the second intermediate transfer member;
Transfer means for transferring the toner image transferred to the surface of the third intermediate transfer member to the surface of the recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
A first cleaning means for cleaning toner remaining on the surface of the first image carrier after transferring the toner image;
A second cleaning means for cleaning toner remaining on the surface of the second image carrier after transferring the toner image;
A third cleaning means for cleaning toner remaining on the surface of the third image carrier after transferring the toner image;
A fourth cleaning means for cleaning the toner remaining on the surface of the fourth image carrier after transferring the toner image;
With
Each of the first developer, the second developer, the third developer, and the fourth developer includes toner containing toner particles and titanium oxide particles externally added to the toner particles; The titanium concentration ratio of the toner contained in the first to fourth developers is the first developer: second developer: third developer: fourth developer = 1.6 to 1.9: 2.0 to 2 .4: 1.2 to 1.5: 0.5 to 1.1,
Image forming apparatus.   An image forming method for forming an image on a recording medium using the image forming apparatus according to claim 6.