JP2007178954A - Yellow toner for electrostatic image development and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a yellow toner for electrostatic image development giving high print density, having a sharp particle size distribution, and excellent in lasting printing property, and a method for manufacturing the same. <P>SOLUTION: The yellow toner for electrostatic image development comprises colored resin particles comprising a binder resin and a yellow colorant, wherein the yellow colorant consists of a yellow pigment (A) of one or more structures, wherein pH of an aqueous suspension of the pigment measured by a boiling method stipulated by an item of pH meters of JIS K5101 is ≥6, and a yellow pigment (B) of one or more structures, wherein pH of an aqueous suspension of the pigment measured by the boiling method is <6. The pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)]-[pH of aqueous suspension of yellow pigment (B)]) is ≥0.5. The method for manufacturing the same is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a yellow toner for developing an electrostatic image used for developing an electrostatic latent image or the like in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like, and a method for producing the same. Hereinafter, the “yellow toner for developing an electrostatic image” may be simply referred to as “yellow toner”.

A method of forming a desired image by developing an electrostatic latent image with toner for developing an electrostatic image is widely used.
For example, in electrophotography, an electrostatic latent image formed on a photoconductor is developed with a toner obtained by blending colored particles with other particles such as an external additive or a carrier as required, and then a paper or an OHP sheet. Then, the toner is fixed to obtain a printed matter.

The manufacturing method of the colored resin particles which are the main constituent elements of the toner is roughly classified into a dry method and a wet method.
An example of the dry method is a pulverization method. The pulverization method is colored by pulverizing and classifying the solids of the colored resin obtained by melt-kneading the binder resin and the colorant, or by polymerizing the mixture containing the polymerizable monomer and the colorant. This is a method for producing resin particles.
On the other hand, examples of the wet method include a polymerization method and a dissolution suspension method.
In the polymerization method, for example, a polymerizable monomer composition containing a polymerizable monomer and a colorant is granulated to form droplets, and the droplets are polymerized to produce colored resin particles. Examples thereof include an emulsion method and an emulsion polymerization aggregation method in which an emulsified polymerizable monomer is polymerized to obtain resin fine particles and aggregated with a colorant or the like to produce colored resin particles.
The dissolution suspension method is a method for producing colored resin particles by granulating a solution in which toner components such as a binder resin and a colorant are dissolved in an organic solvent, and removing the organic solvent.

In recent years, there has been a growing need for colorization of image forming apparatuses such as multifunction machines, facsimiles, and printers using electrophotography.
Color image formation by such a full-color electrophotographic method generally reproduces colors using three color toners of three primary colors, yellow, magenta, and cyan, or four colors including black. In full-color electrophotography, since images such as photographs that require high-resolution and vivid color reproduction are also printed, color toners that can meet these requirements are demanded, and coloring contained in the toners Various studies have been made so far, focusing on agents.
However, conventionally known colorants for yellow toner (hereinafter also referred to as “yellow colorants”) have poor dispersibility in colored resin particles depending on the type of pigment used, so that sufficient printing is possible. Further, when the concentration cannot be achieved, and when it is produced by a polymerization method or a dissolution suspension method, there is a problem that a yellow toner having a wide particle size distribution is generated.

  In Patent Document 1, for the purpose of providing a yellow toner having a high coloring power, a clear color and a good color mixing property, C.I. I. Pigment Yellow 74, C.I. I. A yellow toner characterized by containing at least Pigment Yellow 155 is disclosed.

  Further, in Patent Document 2, for the purpose of providing a yellow toner with less fog and high printing density, the pH of the water extract of the yellow colorant extracted by the hot water extraction method is 6.0-8. A yellow toner, 0, is disclosed.

  However, the yellow toner described in these patent documents cannot be said to have a sufficient print density and durable printability when a large amount of printing is performed.

JP 2005-31163 A JP-A-2005-215234

  The present invention has been made in view of the above circumstances, and since the dispersibility of the colorant is high, the electrostatic charge image development has a high image print density, a sharp toner particle size distribution, and excellent durability printability. An object of the present invention is to provide a yellow toner and a method for producing the same.

As a result of diligent studies to achieve the above object, the present inventors have found that a yellow toner combining two types of yellow pigments having different pHs can achieve the above object. That is, when a pigment having a pH of 6 or more is used as a colorant, colored resin particles having a sharp particle size distribution can be obtained. However, since the dispersibility in the colored resin particles is poor, a high print density cannot be achieved, and the pH is less than 6. When a pigment is used as a colorant, the dispersibility in colored resin particles is high, but the particle size distribution of the resulting yellow toner is not sharp. However, it has been found that by using these two kinds of pigments together, a yellow toner having a high dispersibility of the colorant in the colored resin particles and a sharp particle size distribution can be obtained. .
The present invention has been made on the basis of the above findings, and includes colored resin particles including a binder resin and a yellow colorant,
The yellow colorant is a yellow pigment (A) having a structure of one kind or two kinds or more in which the pH of the aqueous suspension of the pigment is 6 or more as measured by a boiling method defined in the pH meter section of JIS K5101 And a yellow pigment (B) having a structure of one or two or more structures whose pH of the aqueous suspension of the pigment measured by the boiling method is less than 6.
The pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)] − [pH of aqueous suspension of yellow pigment (B)]) is 0. The present invention provides a yellow toner for developing an electrostatic charge image, which is 5 or more.
By using two types of yellow colorants having different pH values as defined above, yellow toner can be obtained with high printing density, sharp particle size distribution, and durable printability.

  Since the yellow colorant according to the present invention can achieve both excellent particle size distribution and printing density, the weight ratio of the added amount of the yellow pigment (A) to the added amount of the yellow pigment (B) ([ The weight of yellow pigment (A)] / [weight of yellow pigment (B)] is preferably 1-10.

  In the yellow toner for developing an electrostatic charge image of the present invention, the content of the yellow colorant is preferably 1 to 15% by weight in the colored resin particles.

  The yellow toner of the present invention is preferably formed by a method including a step of granulating the colored resin particles in an aqueous dispersion medium containing a dispersion stabilizer.

  In the present invention, the colored resin particles contain a polymerizable monomer that is a main component of the monomer constituting the binder resin and the yellow colorant in an aqueous dispersion medium containing a dispersion stabilizer. Yellow toner is preferably formed by forming droplets of the polymerizable monomer composition and then polymerizing the droplets.

  The yellow pigment (A) and the yellow pigment (B) constituting the yellow colorant contained in the yellow toner of the present invention are each one kind of pigment and preferably have the same structure.

  In the present invention, at least one of the yellow pigment (A) and the yellow pigment (B) is C.I. I. Pigment Yellow 74 is preferable.

Further, in the present invention, in the method for producing a yellow toner for developing an electrostatic charge image containing a binder resin and colored resin particles containing a yellow colorant,
As the yellow colorant, one or two or more types of yellow pigments (A) whose pH of an aqueous suspension of the pigment measured by the boiling method defined in the pH meter section of JIS K5101 is 6 or more And a yellow pigment (B) having a structure of one kind or two or more kinds whose pH of the aqueous suspension of the pigment measured by the boiling method is less than 6.
The pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)] − [pH of aqueous suspension of yellow pigment (B)]) is 0. A method for producing a yellow toner for developing an electrostatic charge image is provided.

  In the present invention, a yellow toner for developing an electrostatic image having a high dispersibility of a yellow colorant and a sharp particle size distribution can be obtained. Therefore, even if a large amount of printing is performed, fogging does not occur, and high-quality printing with a high printing density can be performed.

  The yellow toner for developing an electrostatic charge image of the present invention contains colored resin particles containing a binder resin and a yellow colorant, and the yellow colorant is measured by a boiling method defined in the pH meter section of JIS K5101. The yellow pigment (A) having one or two or more structures whose pH of the aqueous suspension of the pigment to be used is 6 or more, and the pH of the aqueous suspension of the pigment measured by the boiling method is less than 6 A yellow pigment (B) having one or more structures, and a pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)]) -[PH of aqueous suspension of yellow pigment (B)]) is 0.5 or more.

Hereinafter, the constituent material and manufacturing method of the yellow toner of the present invention will be described in detail.
The yellow toner for developing an electrostatic charge image of the present invention contains colored resin particles, and if necessary, other particles such as an external additive attached to the surface of the colored resin particles and a carrier which is a particle supporting the colored resin particles. Or you may contain the component.
The colored resin particles in the yellow toner contain a binder resin and a yellow colorant, and may contain other components such as a charge control agent and a release agent as necessary.

  As the binder resin contained in the colored resin particles, resins conventionally used as a binder resin for toner can be used. For example, styrene such as polystyrene and polyvinyltoluene, and substituted polymers thereof; styrene-methyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-ethyl acrylate 2-ethylhexyl copolymer, styrene-methacryl Styrene copolymers such as acid methyl copolymer, styrene ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, and styrene-butadiene copolymer; polymethyl methacrylate, polyester, epoxy resin, polyvinyl butyral, fat And hydrogenated products of aliphatic or alicyclic hydrocarbon resins, polyolefins, acrylate resins, methacrylate resins, norbornene resins, and styrene resins.

The yellow colorant according to the present invention comprises at least one yellow pigment selected from yellow pigments having a pH of an aqueous pigment suspension of 6 or more as measured by a boiling method defined in the pH meter section of JIS K5101. The pigment (A) and at least one or more yellow pigments (B) selected from yellow pigments whose pH of the aqueous pigment suspension measured by the boiling method is less than 6.
When only the yellow pigment (A) having a pH of 6 or higher is used, colored resin particles having a sharp particle size distribution can be obtained, but dispersibility in the colored resin particles tends to deteriorate.
On the other hand, when only the yellow pigment (B) having a pH of less than 6 is used, the dispersibility of the colorant increases. However, when the yellow toner is prepared, the liquid of the polymerizable monomer composition is caused by the acidity of the colorant. Since the droplets become unstable, a particle size distribution is widened, and a toner having a low circularity is easily obtained.
However, by combining the yellow pigment (A) and the yellow pigment (B) as a yellow colorant, a yellow toner having a sharp particle size distribution and a high dispersibility of the colorant is obtained.
“One kind of yellow pigment” refers to a yellow toner having the “same structure” as described later. That is, this “seed” relates to the “structure” of the yellow pigment.

In the present invention, the pH of the aqueous suspension of the pigment measured by the boiling method of the yellow pigment (A) is 6 or more, more preferably 6.5 or more.
On the other hand, the pH of the aqueous pigment suspension measured by the boiling method of the yellow pigment (B) is less than 6, more preferably less than 5.0.
Further, the pH difference between the yellow colorant (A) and the yellow colorant (B) ([pH of aqueous suspension of yellow pigment (A)] − [pH of aqueous suspension of yellow pigment (B)) ]) Is 0.5 or more, more preferably 1.0 or more. By setting the difference in pH between the yellow pigment (A) and the yellow pigment (B) within the above range, a sufficient print density can be obtained, and a yellow toner having a sharp particle size distribution and excellent durability printability can be obtained. .

In the present invention, the weight ratio of the addition amount of the yellow pigment (A) to the yellow pigment (B) ([weight of yellow pigment (A)] / [weight of yellow pigment (B)]) is 1 to 10. It is preferable that it is 2-8.
When the weight ratio is less than 1, yellow toner having a wide particle size distribution is likely to be obtained, and the durability printability may be deteriorated.
On the other hand, if the weight ratio exceeds 10, the dispersibility of the yellow colorant in the colored resin particles tends to be lowered, so that a sufficient print density may not be achieved.

Among the pigments, the yellow pigment (A) and the yellow pigment (B) are each preferably one type of pigment, that is, a pigment having the same structure, and more preferably both the pigments have the same structure.
In the present invention, the “same structure” pigment is a pigment having the same main skeleton constituting the pigment molecule. Typically, pigments having the same chemical structure including substituents and different pH are combined. Even if the chemical structure of the pigment is completely the same, pigments having different pHs can be obtained by subjecting the pigment to different surface treatments. The same C.I. in the color index (C.I .: The Society of Dyers and Colorists). I. The pigments to which the Pigment number is assigned have the same chemical structure, but there may be a type of pigment having a different pH.

  Examples of pigments having a different pH even if the chemical structures are completely the same include C.I. having a monoazo skeleton. I. Pigment Yellow 74, Fast Yellow 7415 (trade name, manufactured by Sanyo Dye) and Fast Yellow 7416 (trade name, manufactured by Sanyo Dye) have the same CI Pigment number and are identical to those shown below. Has a chemical structure. However, the pH of Fast Yellow 7415 (trade name, manufactured by Sanyo Dye) is 7.1 due to the difference in surface treatment, and the pH of Fast Yellow 7416 (trade name, manufactured by Sanyo Dye) is 4. 2.

  In addition, pigments that have the same chemical structure as described above but differ in pH, for example, contact the surface of the colorant with an acid such as sulfuric acid, nitric acid or hydrochloric acid, or a base such as sodium hydroxide or potassium hydroxide. It is also prepared by a method of treating with a rosin, a method of treating with a fatty acid or a salt thereof, a method of treating with a polymer, a method of chemically treating the surface by local oxidation with an oxidizing agent or low-temperature plasma, etc. be able to.

The yellow pigment (A) and the yellow pigment (B) constituting the yellow colorant can be used without any particular limitation as long as the pH specified in the present invention is satisfied. Compounds such as pigments and condensed polycyclic pigments can be used. Specifically, C.I. I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 75, 83, 90, 93, 97, 120, 138, 155, 180, 181, 185, and 186. In the present invention, at least one of the yellow pigment (A) and the yellow pigment (B) is C.I. I. Pigment Yellow 74, 120, 180, and 185 are preferable. I. Pigment Yellow 74 or 180 is more preferable.
In the present invention, a pigment other than the yellow pigment may be supplementarily included in the colored resin particles in order to adjust the color and transparency of the yellow toner.

  The amount of the yellow colorant is preferably 1 to 15% by weight and more preferably 3 to 12% by weight in the colored resin particles. When the amount of the yellow colorant exceeds the above range, the minimum fixing temperature of the toner is increased and fogging is likely to occur. On the other hand, if it is less than the above range, sufficient print density cannot be obtained.

The pH of the yellow colorant is determined by a method specified by JIS K5101-26.3.3.1-1991.
JIS K5101-26.3.3.1-1991 is a reproduction of pH defined by JIS Z 8802-1958, which is composed of a detection unit composed of a glass electrode and a comparison electrode, and an instruction unit that displays the detected potential difference. The pH of an aqueous pigment suspension is measured using a pH meter having a property within ± 0.02, ± 0.05, or ± 0.1, and the boiling method described below is used.

In the boiling method, 5 g of a sample (in the present invention, yellow pigment) is weighed to the first decimal place in a 300 mL Erlenmeyer flask, and then purified by distillation or ion exchange is boiled for about 5 minutes. Add 100 mL of water from which dissolved carbon dioxide has been degassed, heat it for about 5 minutes with the stopper removed, and boil it for 5 minutes. When the sample is difficult to disperse, add 5-10 mL of 95% purity ethanol specified in JIS K 8102-1994 as a wetting agent to the Erlenmeyer flask and thoroughly disperse the sample. Water is added so that the liquid volume becomes 100 mL.
After boiling for 5 minutes, cap the Erlenmeyer flask, let it cool to room temperature, open the stopper, add water corresponding to the amount reduced by boiling, cover again and shake for 1 minute, then leave for 5 minutes This is used as an aqueous suspension of the sample.

The pH of the aqueous suspension of the pigment treated by the above method is measured by a pH meter using a glass electrode as follows according to the measurement method specified in 7 of JIS Z 8802-1958.
First, the pH meter is adjusted after the electrode has been washed by the method specified in 7 of JIS Z 8802-1958.
Next, take an aqueous suspension prepared by the above method with a volume of 10 to 25 mL so that the measured value does not change, so that the temperature of the aqueous suspension does not change more than ± 0.1 ° C., The measurement is performed with a pH meter having a glass electrode defined in JIS Z 8802-1958 described above. Depending on the reproducibility of the pH meter used, the values measured three times are averaged until they agree within a range of ± 0.02, ± 0.05, or ± 0.1, respectively. And the pH of the yellow pigment.

  The colored resin particles preferably contain a charge control agent. As the charge control agent, a charge control agent conventionally used for toner can be used without any limitation. As the charge control agent, there are a negative charge control agent and a positive charge control agent, which are selectively used depending on whether the toner of the present invention is a negatively chargeable toner or a positively chargeable toner.

Among the charge control agents, it is preferable to use a charge control resin. The charge control resin has high compatibility with the binder resin, is colorless, and a toner having stable chargeability can be obtained even in continuous color printing at high speed.
Hereinafter, the negative charge control resin and the positive charge control resin will be described.

  Examples of the negative charge control resin include a resin having a substituent selected from a carboxyl group or a salt thereof, a phenol group or a salt thereof, a thiophenol group or a salt thereof, a sulfonic acid group or a salt thereof in a polymer side chain. Is mentioned.

Among these, a resin having a sulfonic acid group or its base in the side chain of the polymer is preferably used. Specific examples include a resin obtained by copolymerizing a monovinyl monomer containing a sulfonic acid group or a base thereof and another monovinyl monomer copolymerizable with the monovinyl monomer.
Examples of monovinyl monomers containing a sulfonic acid group or its base include styrene sulfonic acid, sodium styrene sulfonate, potassium styrene sulfonate, 2-acrylamido-2-methylpropane sulfonic acid, sodium vinyl sulfonate, and methacryl sulfone. An ammonium acid etc. are mentioned.
Other monovinyl monomers that can be copolymerized with the monovinyl monomer containing the sulfonic acid group or its base include ethylenically unsaturated carboxylic acid ester monomers, aromatic vinyl monomers, and ethylenic monomers. Examples thereof include unsaturated nitrile monomers.

  The blending amount of the monovinyl monomer containing a sulfonic acid group or a base thereof is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight in all monomers constituting the negative charge control resin. %. When the blending amount of the monovinyl monomer containing a sulfonic acid group or its base is less than the above range, the charge amount of the toner may be insufficient. When the blending amount exceeds the above range, the toner charge under a low temperature and low humidity condition may occur. The increase in the amount becomes large, and printing stains may occur.

The negative charge control resin preferably has a weight average molecular weight of 2,000 to 50,000, more preferably 4,000 to 40,000, and most preferably 6,000 to 35,000.
The glass transition temperature of the negative charge control resin is preferably 40 to 80 ° C, more preferably 45 to 75 ° C, and most preferably 45 to 70 ° C. When the glass transition temperature is less than the above range, the storage stability of the toner is deteriorated, and when it exceeds the above range, the fixability may be lowered.

The positive charge control resin, for _{example, -NH 2, -NHCH 3, -N} (CH 3) 2, -NHC 2 H 5, -N (C 2 H5) 2, -NHC 2 H 4 amino group of OH, etc. And resins containing functional groups in which they are ammonium chlorided. Such a resin is obtained, for example, by copolymerizing a monovinyl monomer containing an amino group and a monovinyl monomer copolymerizable therewith. Further, the copolymer obtained as described above can be obtained by ammonium chloride. Furthermore, although obtained by copolymerizing a monovinyl monomer containing an ammonium salt group and a monovinyl monomer copolymerizable therewith, it is not limited to these methods. As a monovinyl monomer copolymerizable with a monovinyl monomer containing an amino group or a monovinyl monomer copolymerizable with a monovinyl monomer containing an ammonium salt group, a negatively chargeable control resin is obtained. For that purpose.

  Examples of monovinyl monomers containing amino groups include acrylamide monomers such as acrylamide, N-methylacrylamide, N, N-dimethylacrylamide, and N-ethylacrylamide; 3- (dimethylamino) propyl acrylate Acrylic acid derivatives such as: methacrylamide, N-methylmethacrylamide, N, N-dimethylmethacrylamide, and other methacrylamide monomers such as N-ethylmethacrylamide; 3- (dimethylamino) propyl methacrylate, etc. Methacrylic acid-based derivatives; allylamine; styrene-based derivatives such as 2-aminostyrene and 4-aminostyrene.

  As the ammonium reagent used for ammonium-salting the copolymer, those commonly used are used, for example, alkyl halides such as methyl iodide, ethyl iodide, methyl bromide, and ethyl bromide; Examples include paratoluenesulfonic acid alkyl esters such as methyl toluenesulfonate, ethyl paratoluenesulfonate, and propyl paratoluenesulfonate.

  The blending amount of the monovinyl monomer having a functional group such as an amino group and an ammonium salt group is preferably 0.5 to 15% by weight, more preferably in all monomers constituting the positive charge control resin. 1 to 10% by weight. If the amount of the monovinyl monomer having a functional group is less than the above range, the charge amount of the toner may be insufficient. If the amount exceeds the above range, the increase in the charge amount of the toner under low temperature and low humidity is large. In some cases, printing stains may occur.

The positive charge control resin preferably has a weight average molecular weight of 2,000 to 30,000, more preferably 4,000 to 25,000, and most preferably 6,000 to 20,000.
The glass transition temperature of the positive charge control resin is preferably 40 to 100 ° C, more preferably 45 to 80 ° C, and most preferably 45 to 70 ° C. When the glass transition temperature is less than the above range, the storage stability of the toner is deteriorated, and when it exceeds the above range, the fixability may be lowered.
The amount of the charge control agent used is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer used to obtain the binder resin.

The colored resin particles preferably contain a release agent. Examples of the release agent include polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; natural waxes such as candelilla, carnauba, rice, wood wax, and jojoba; paraffin, microcrystalline, and petrolactam Petroleum wax and modified wax thereof; synthetic wax such as Fischer-Tropsch wax; pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrapalmitate, dipentaerythritol hexamyristate, dipentaerythritol hexastearate, etc. And the like.
A mold release agent can be used 1 type or in combination of 2 or more types.
The amount of the release agent is usually 0.5 to 50 parts by weight, preferably 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

  In the present invention, the colored resin particles are preferably so-called core-shell type particles obtained by combining two different polymers on the inside (core layer) and outside (shell layer) of the particles. In the core-shell type particles, the low softening point material in the inside (core layer) is coated with a material having a higher softening point, so that it is possible to balance the lowering of the minimum fixing temperature and the storage stability of the toner. It is.

  In the present invention, the volume average particle diameter (Dv) of the colored resin particles is preferably 4 to 10 μm, and more preferably 4 to 7 μm. If Dv is less than the above range, the fluidity of the toner becomes small, fogging may occur, transfer residue may occur, and cleaning properties may deteriorate. On the other hand, if Dv exceeds the above range, fine line reproducibility may be deteriorated and high image quality may not be achieved, or fixability may be deteriorated.

  The ratio Dv / Dp between the number average particle diameter (Dp) and the volume average particle diameter (Dv) of the colored resin particles is preferably 1.0 to 1.3, and preferably 1.0 to 1.2. More preferably. When the ratio Dv / Dp is out of the above range, there are cases where blurring occurs when printing is performed using the obtained polymerized toner, and transferability, printing density and resolution are reduced. The volume average particle diameter (Dv) and the number average particle diameter (Dp) of the colored resin particles can be measured using, for example, Multisizer (trade name, manufactured by Beckman Coulter, Inc.).

The average circularity (Ca) of the colored resin particles is preferably 0.950 to 0.990, and more preferably 0.970 to 0.988. When the average circularity is within this range, an image excellent in fine line reproducibility can be obtained.
In the present invention, the circularity is defined as a value obtained by dividing the circumference of a circle having the same projected area as the particle image by the circumference of the projected image of the particle. Further, the circularity is used as a simple method for quantitatively expressing the shape of the particles, and is an index indicating the degree of unevenness of the colored resin particles, and the average circularity is a perfect spherical shape of the colored resin particles. 1 is shown in the case, and the value becomes smaller as the surface shape of the colored resin particles becomes more complicated. For the average circularity (Ca), first, the circularity (Ci) of each particle measured for a particle group having a circle-equivalent diameter of 1 μm or more is obtained from the following equation for n particles, and then obtained by the following equation.
Circularity (Ci) = perimeter of circle equal to projected area of particle / perimeter of projected particle image

In the above formula, fi is the frequency of particles having a circularity Ci.
The average circularity can be measured using a flow type particle image analyzer “FPIA-2100” (trade name) or “FPIA-3000” (trade name) manufactured by Sysmex Corporation.

The colored resin particles according to the present invention can be produced by a conventionally known method such as a dry method and a wet method.
An example of the dry method is a pulverization method. The pulverization method produces colored resin particles by pulverizing and classifying solids of the colored resin obtained by melt kneading the binder resin and the colorant or polymerizing the mixture containing the monomer and the colorant. It is a method to do.
On the other hand, examples of the wet method include a polymerization method and a dissolution suspension method. The polymerization method includes, for example, granulating a polymerizable monomer composition containing a polymerizable monomer and a colorant to form droplets. Suspension polymerization method for forming colored resin particles by forming and polymerizing the droplets, or polymerizing emulsified polymerizable monomers to obtain resin fine particles, and agglomerating with a colorant or the like to form colored resin particles An emulsion polymerization aggregation method for producing
The dissolution suspension method is a method for producing colored resin particles by granulating a solution in which toner components such as a binder resin and a colorant are dissolved in an organic solvent, and removing the organic solvent.
Among the above production methods, since colored resin particles having a sharp particle size distribution can be obtained, it is preferable to produce colored resin particles by a wet method, and among the wet methods, the organic solvent can be removed by the dissolution suspension method. The polymerization method is more preferable because it is necessary, and the emulsion polymerization aggregation method requires the removal of the emulsifier, so that it is particularly preferably produced by a suspension polymerization method.

  In the case of the suspension polymerization method, first, a yellow colorant and, if necessary, other components such as a charge control agent and a release agent are dissolved or dispersed in the polymerizable monomer that is a raw material of the binder resin. To prepare a polymerizable monomer composition. Next, after adding the polymerizable monomer composition to an aqueous dispersion medium containing a dispersion stabilizer, droplets of the polymerizable monomer composition are formed. The dispersion can be produced by adding a polymerization initiator to the dispersion containing the droplets, polymerizing the particles, and associating the particles as necessary, followed by filtration, washing, dehydration and drying.

  In the method for producing a toner for developing an electrostatic charge image according to the present invention, it is preferable to uniformly disperse and refine the colorant particles. As a method for dispersing and refining the colorant particles, it is preferable to perform a dispersion step on the polymerizable monomer composition. Specifically, a yellow colorant, a monovinyl monomer, and, if necessary, a part of other components are dispersed by a media type dispersing machine. By performing the dispersion step, the dispersibility of the yellow colorant can be improved, so that a yellow toner having a high printing density can be obtained.

  Further, when producing core-shell type colored resin particles, the colored resin particles obtained by any of the above methods are used as a core layer, and spray drying method, interfacial reaction method, in situ polymerization method, layer separation method, etc. The shell layer is coated by a conventionally known method. Preferably, the colored resin particles produced by the polymerization method are coated with the shell layer by the in situ polymerization method.

Examples of the monovinyl monomer include styrene; styrene derivatives such as vinyl toluene and α-methylstyrene; acrylic acid and methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, acrylic acid 2 Acrylic esters such as ethylhexyl and dimethylaminoethyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and dimethylaminoethyl methacrylate; acrylamide Amide compounds of acrylic acid such as methacrylamide, amides of methacrylic acid; olefins such as ethylene, propylene and butylene; halogens such as vinyl chloride, vinylidene chloride and vinyl fluoride Vinyl esters such as vinyl acetate and vinylidene halides; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone and methyl isopropenyl ketone; 2-vinyl pyridine, 4 -Nitrogen-containing vinyl compounds such as vinyl pyridine and N-vinyl pyrrolidone; These monovinyl monomers may be used alone or in combination. Of these, styrene, styrene derivatives, and acrylic acid or methacrylic acid derivatives are preferably used as monovinyl monomers.
The proportion of the monovinyl monomer is preferably at least 80% by weight or more in the polymerizable monomer used to form the binder resin component.

  In order to improve hot offset, it is preferable to use any crosslinkable monomer together with the monovinyl monomer. A crosslinkable monomer refers to a monomer having two or more polymerizable functional groups. Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof. These crosslinkable monomers can be used alone or in combination of two or more.

Furthermore, it is preferable to use a macromonomer as a part of the polymerizable monomer because the balance between the storage stability and the fixing property at a low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is a reactive oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000.
The macromonomer is preferably one that gives a polymer having a higher Tg than the Tg of the polymer obtained by polymerizing the monovinyl monomer. The amount of the macromonomer is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the monovinyl monomer.

Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; Inorganic compounds that can be dissolved in acids or alkalis such as metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide. Furthermore, organic compounds such as water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants; nonionic surfactants; amphoteric surfactants; The said dispersion stabilizer can be used 1 type or in combination of 2 or more types.
Among the above dispersion stabilizers, dispersion stabilizers containing colloids of metal compounds, particularly poorly water-soluble metal hydroxides, can narrow the particle size distribution of the colored resin particles, and the dispersion stabilizer remains after washing. Since the amount is small, the obtained polymerized toner is preferable because the image can be clearly reproduced and the environmental stability is not deteriorated.
The dispersion stabilizer is used in an amount of 0.1 to 20 parts, preferably 0.2 to 10 parts, based on 100 parts of the aqueous dispersion medium.

In the present invention, examples of the polymerization initiator for polymerizing the polymerizable monomer composition include persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid). 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4- Dimethylvaleronitrile) and azo compounds such as 2,2′-azobisisobutyronitrile; di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexyl Peroxy-2-ethylhexanoate, t-butyl peroxypivalate, diisopropyl peroxydicarbonate, di-t-butylperoxy Sofutareto, and t- butyl organic peroxide peroxy isobutyrate and the like. Moreover, you may use the redox initiator which combined the said polymerization initiator and the reducing agent. Among these, it is preferable to use an organic peroxide because residual polymerizable monomers can be reduced and printing durability is good.
As described above, the polymerization initiator may be added after the polymerizable monomer composition is dispersed in the aqueous medium and before droplet formation, but is added to the polymerizable monomer composition. May be.
The addition amount of the polymerization initiator used for polymerization of the polymerizable monomer composition is preferably 0.1 to 20 parts by weight, more preferably 0.3 to 100 parts by weight of the monovinyl monomer. -15 parts by weight, most preferably 1.0-10 parts by weight.

  Furthermore, it is preferable to use a molecular weight modifier in the polymerization. Examples of molecular weight modifiers include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol. The molecular weight modifier can be added before the start of polymerization or during the polymerization. The amount of the molecular weight modifier is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the monovinyl monomer.

  As the polymerizable monomer for the shell, the same monomers as the aforementioned polymerizable monomers can be used. Among these, it is preferable to use monomers such as styrene, acrylonitrile, and methyl methacrylate that can yield a polymer having a Tg exceeding 80 ° C. alone or in combination of two or more.

  As polymerization initiators used for polymerization of the polymerizable monomer for shell, potassium persulfate and persulfate metal salts such as ammonium persulfate; 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) Propionamide], and azo-based initiators such as 2,2′-azobis- {2-methyl-N- [1,1-bis (hydroxymethyl) 2-hydroxyethyl] propionamide}; An agent can be mentioned. The amount of the polymerization initiator is preferably 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer for shell.

  In the present invention, the colored resin particles obtained by the above method, preferably the core-shell type colored resin particles, to which an external additive is attached can be used as a one-component toner. Furthermore, the colored resin particles can be used as a two-component toner by mixing other fine particles such as a carrier using a mixer such as a V-type mixer.

By attaching or embedding an external additive on the surface of the colored resin particles, the chargeability, fluidity, storage stability, etc. of the toner can be adjusted.
As the external additive, any external additive conventionally used in toners can be used without any limitation, and examples thereof include inorganic particles and organic resin particles. Examples of inorganic particles include silica, aluminum oxide, titanium oxide, zinc oxide, and tin oxide. Examples of organic resin particles include acrylic acid ester polymer particles, methacrylic acid ester polymer particles, and styrene-acrylic acid esters. Examples thereof include copolymer particles and styrene-methacrylic acid copolymer particles. Of these, silica and titanium oxide are preferred, those having the surface of the particles treated with hydrophobic treatment are preferred, and silica particles treated with hydrophobic treatment are particularly preferred.
The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight with respect to 100 parts by weight of the colored resin particles.

As the carrier, any carrier conventionally used in toners can be used without any limitation. For example, magnetic powder such as iron powder, ferrite powder, and nickel powder, glass beads, etc. And those treated with a surface treatment with a styrene resin, a styrene / acrylic resin, a silicone resin, or the like.
In the case of a two-component toner, the concentration of the colored particles in the toner is usually 0.1 to 50% by weight, preferably 0.5 to 15% by weight, and more preferably 3 to 10% by weight.

  The yellow toner of the present invention as described above is used to develop a latent image having electrostatic characteristics of an electrostatic latent image in electrophotography, electrostatic recording method, electrostatic printing method, etc. Widely used in electrostatic latent image developing systems, developing methods, and image forming apparatuses for forming images such as symbols.

  The yellow toner provided by the present invention has high print density due to high dispersibility of the yellow colorant, sharp particle size distribution, and is excellent in durable printability with little fog even when printing in large quantities. Therefore, a high quality image can be formed over a long period of time.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples. Parts and% are based on weight unless otherwise specified.

[Example 1]
As a monovinyl monomer, 82 parts of styrene, 18 parts of n-butyl acrylate, a yellow pigment (A) having a pH of 6 or more, C.I. I. Pigment Yellow 74 (trade name “Fast Yellow 7415”, manufactured by Sanyo Color Co., Ltd., pH = 7.1), 5 parts, and a yellow pigment (B) having a pH of less than 6, C.I. I. 1 part of Pigment Yellow 74 (trade name “Fast Yellow 7416”, manufactured by Sanyo Dye Co., Ltd., pH = 4.2) is dispersed using a media-type disperser, and a polymethacrylate macromonomer (Toagosei Co., Ltd.) is used as the macromonomer. Made by Kogyo Co., Ltd., trade name “AA6”, Tg = 94 ° C., 0.5 part, cross-linkable monomer, 0.7 part divinylbenzene, molecular weight regulator, 1 part t-dodecyl mercaptan, negative charge control resin (Fujikura) 1 part of Kasei Chemicals, trade name “FCA-207P”) and 6 parts of dipentaerythritol hexamyristate (maximum thermal peak is 66.2 ° C., molecular weight 1514) as a release agent are added. A body composition was obtained.

  Meanwhile, an aqueous solution in which 12 parts of magnesium chloride (water-soluble polyvalent metal salt) is dissolved in 280 parts of ion-exchanged water and an aqueous solution in which 6 parts of sodium hydroxide (alkali metal hydroxide) are dissolved in 60 parts of ion-exchanged water are stirred. The mixture was gradually added while preparing a magnesium hydroxide colloid (colloid of poorly water-soluble metal hydroxide) dispersion.

  The above polymerizable monomer composition is added to the magnesium hydroxide colloidal dispersion obtained as described above, and after stirring, t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, Further, 5 parts of a product name “Perbutyl O”) was added, and high shear stirring was performed for 10 minutes at a rotational speed of 15,000 rpm using an in-line type emulsifying disperser (product name “Ebara Milder” manufactured by Ebara Seisakusho) Thus, droplets of the polymerizable monomer composition were formed.

  An aqueous dispersion in which droplets of the polymerizable monomer composition were dispersed was put into a reactor equipped with a stirring blade, and the temperature was raised to 90 ° C. to carry out a polymerization reaction. After the polymerization conversion reached almost 100%, the polymerization temperature was kept as it was, and 2,2′-azobis [2 dissolved in 1 part of methyl methacrylate as a shell polymerizable monomer and 10 parts of ion-exchanged water. -Methyl-N- (2-hydroxyethyl) propionamide] (manufactured by Wako Pure Chemical Industries, trade name “VA086”) 0.1 part was added, and the reaction was continued at 90 ° C. for 3 hours, followed by water cooling. An aqueous dispersion of colored resin particles having a core-shell structure was obtained. The pH of the aqueous dispersion was 9.5.

  While stirring the aqueous dispersion of the colored resin particles obtained as described above, sulfuric acid was added until the pH became 6 or less, and stirring was continued for 10 minutes at 25 ° C. Then, after separating water by filtration, 500 parts of ion-exchanged water was newly added to form a slurry again, followed by water washing with stirring for 10 minutes. Then, after repeating dehydration and water washing several times again, the colored resin particles were separated by filtration to obtain wet colored resin particles. The wet colored resin particles were put in a dryer and dried at 40 ° C. for 3 days.

  To 100 parts of the colored resin particles obtained as described above, 1 part of silica fine particles hydrophobized with a number primary average particle diameter of 7 nm and 1 part of silica fine particles hydrophobized with a number primary average particle diameter of 35 nm are added, The toner of Example 1 was obtained by mixing using a high-speed stirrer (trade name “Henschel Mixer” manufactured by Mitsui Mining Co., Ltd.).

[Example 2]
In Example 1 above, as a yellow pigment (A) having a pH of 6 or more, C.I. I. Pigment Yellow 74 (trade name “Fast Yellow 7415” manufactured by Sanyo Dyeing Co., Ltd.) and yellow pigment (B) having a pH of less than 6 include C.I. I. A toner of Example 2 was obtained in the same manner as in Example 1 except that 2 parts of Pigment Yellow 74 (trade name “Fast Yellow 7416”, manufactured by Sanyo Color Co., Ltd.) were used.

Example 3
In Example 1 above, as a yellow pigment (A) having a pH of 6 or more, C.I. I. A toner of Example 3 was obtained in the same manner as in Example 1 except that 5 parts of Pigment Yellow 180 (manufactured by Clariant Japan, trade name “Toer Yellow HG”, pH = 6.8) was used.

[Comparative Example 1]
In Example 1 above, as a yellow colorant, as a yellow pigment (A) having a pH of 6 or more, C.I. I. A toner of Comparative Example 1 was obtained in the same manner as in Example 1 except that only 6 parts of Pigment Yellow 74 (trade name “Fast Yellow 7415”, manufactured by Sanyo Color Co., Ltd., pH = 7.1) was used.

[Comparative Example 2]
In Example 1 above, as a yellow pigment (B) having a pH of less than 6 as a yellow colorant, C.I. I. A toner of Comparative Example 2 was obtained in the same manner as in Example 1 except that only 6 parts of Pigment Yellow 74 (trade name “Fast Yellow 7416”, manufactured by Sanyo Dye Co., Ltd., pH = 4.2) was used.

〔Test method〕
For each toner, the volume average particle diameter (μm) and the number average particle diameter (Dp) were measured. Moreover, the pH of the used yellow pigment (A) and yellow pigment (B) was measured.
Regarding the printing performance, an initial printing density and a durable printing test were conducted.
The test methods performed in this example are as follows.

(1) Measurement of pH of yellow colorant The pH of the yellow colorant used in this example is JIS K5101-26. Based on the method defined in -1991, an aqueous pigment suspension was measured by the boiling method of 3.1 as follows.
Weigh 5 g of yellow pigment in a 300 mL Erlenmeyer flask up to the first digit of the decimal point, boil the purified product by distillation or ion exchange for about 5 minutes, and add 100 mL of water degassed dissolved carbon dioxide. In addition, after boiling for about 5 minutes with the stopper removed, the mixture was further boiled for 5 minutes. If it is difficult to disperse the pigment, add 5-10 mL of ethanol (95) (95% purity ethanol) specified in JIS K 8102-1994 as a wetting agent to the Erlenmeyer flask, and disperse the sample well. After that, water was added so that the amount of the liquid added including ethanol was 100 mL.
After boiling for 5 minutes, cap the Erlenmeyer flask and let it cool to room temperature, then open the stopper and add water corresponding to the amount reduced by boiling. This was used as an aqueous suspension in which the pigment was dispersed.

The pH of the aqueous suspension thus prepared was measured by the measuring method specified in 7 of JIS Z 8802-1958.
First, a pH meter (trade name “F-51” manufactured by HORIBA Co., Ltd.) was adjusted for the washed electrode according to the method defined in 7 of JIS Z 8802-1958.
Next, take an aqueous suspension of pigment prepared by the above method in an amount of 10 to 25 mL so that the measured value does not change, and the temperature of the aqueous suspension of pigment does not change more than ± 0.1 ° C. Thus, the measurement was performed using the pH meter, and the values obtained until the three consecutive measurements were matched within a range of ± 0.02 were averaged to obtain the pH of the yellow pigment.

(2) Measurement of particle diameter Volume average particle diameter (Dv) and number average particle diameter (Dp) were measured by a particle diameter measuring machine (trade name “Multisizer” manufactured by Beckman Coulter, Inc.). The measurement with this multisizer was performed under the conditions of aperture diameter: 100 μm, medium: Isoton II, and number of measured particles: 100,000.

(3) Evaluation of initial print density Put toner into a commercially available non-magnetic one-component development printer (20 sheets machine), print continuously from the beginning at 5% print density, and perform solid print when printing the 10th sheet. The initial printing density was measured using a reflection type image density measuring machine. Usually, the initial printing density is preferably in the range of 1.35 to 1.45.

(4) Initial printing test Printing paper was set in the printer used in the above (3), toner was put in the developing device, and fog was measured as follows.
White solid print (0% print density) is performed, and the printer is stopped at about 10 prints on the way. The toner on the non-image area is applied to the developed photoconductor with adhesive tape (manufactured by Sumitomo 3M Limited, product) Name “Scotch Mending Tape 810-3-18”). This adhesive tape was affixed to a new printing paper, and the color tone was measured with a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name “SE-2000”). As a reference (reference sample), an unused adhesive tape was affixed to printing paper, and the color tone was measured in the same manner. Each color tone is expressed as coordinates in the L * a * b * space, and a color difference ΔE is calculated from the color tone of the measurement sample and the reference sample to obtain a fog value. The smaller this value is, the smaller the fog is. If the fog value ΔE is 1.0 or less, the image quality is good.

(5) Durability printing test Set printing paper in the printer used in (3) above, put toner in the developing device, perform continuous printing at 1% printing density, and perform fogging to print up to 20,000 sheets. Was measured as follows.
White solid printing (0% printing density) is performed, and after printing 20,000 sheets, the toner in the non-image area on the developed photoreceptor is adhesive tape (manufactured by Sumitomo 3M Co., Ltd., trade name “Scotch Mending Tape 810”). -3-18 "). This adhesive tape was affixed to a new printing paper, and the color tone was measured with a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name “SE-2000”). As a reference (reference sample), an unused adhesive tape was affixed to printing paper, and the color tone was measured in the same manner. Each color tone is expressed as coordinates in the L * a * b * space, and a color difference ΔE is calculated from the color tone of the measurement sample and the reference sample to obtain a fog value. Smaller values indicate less fog and better image quality. The smaller this value is, the smaller the fog is. If the fog value ΔE is 1.0 or less, the image quality is good.

〔result〕
The test results are shown in Table 1.
The notes in Table 1 are as follows.
* 1: Abbreviations for binder resin ST (styrene), BA (n-butyl acrylate), DVB (divinylbenzene),
* 2: Abbreviations for colorants PY74 (C.I. Pigment Yellow 74), PY180 (C.I. Pigment Yellow 180)

[Summary of results]
As the yellow colorant, the toners of Examples 1 to 3 using two types of yellow pigment (A) having a pH of 6 or more and yellow pigment (B) having a pH of 6 or less have high print density, initial printing, and Since no fogging occurred even after printing 20,000 sheets, the toner was excellent in printing performance.
On the other hand, the toner of Comparative Example 1 using only the yellow pigment (A) having a pH of 6 or higher had a poor dispersibility of the colorant, so that a sufficient print density was not obtained and the durable printability was also lowered. Further, the toner of Comparative Example 2 using only the yellow pigment (B) having a pH of 6 or less as the yellow colorant has a high Dv / Dp, so that the particle size distribution of the obtained toner is disturbed. Fog was confirmed after printing 000 sheets.

Claims (8)

Containing colored resin particles containing a binder resin and a yellow colorant;
The yellow colorant is a yellow pigment (A) having a structure of one kind or two kinds or more in which the pH of the aqueous suspension of the pigment is 6 or more as measured by a boiling method defined in the pH meter section of JIS K5101 And a yellow pigment (B) having a structure of one or two or more structures whose pH of the aqueous suspension of the pigment measured by the boiling method is less than 6.
The pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)] − [pH of aqueous suspension of yellow pigment (B)]) is 0. A yellow toner for developing an electrostatic charge image, wherein the yellow toner is 5 or more.   The weight ratio of the addition amount of the yellow pigment (A) to the addition amount of the yellow pigment (B) ([weight of yellow pigment (A)] / [weight of yellow pigment (B)]) is 1 to 10. The yellow toner for developing electrostatic images according to claim 1.   3. The yellow toner for developing electrostatic images according to claim 1, wherein the content of the yellow colorant is 1 to 15 wt% in the colored resin particles.   4. The electrostatic image developing yellow according to claim 1, wherein the colored resin particles are formed by a method including a step of granulating in an aqueous dispersion medium containing a dispersion stabilizer. toner.   A polymerizable monomer containing the polymerizable monomer as a main component of the monomer constituting the binder resin in the aqueous dispersion medium containing the dispersion stabilizer, and the yellow colorant. The yellow toner for developing an electrostatic charge image according to claim 1, wherein the droplet is formed by polymerizing the droplet after forming the droplet of the body composition.   6. The electrostatic image developing yellow according to claim 1, wherein each of the yellow pigment (A) and the yellow pigment (B) is one kind of pigment and has the same structure. toner.   At least one of the yellow pigment (A) and the yellow pigment (B) is C.I. I. The yellow toner for developing electrostatic images according to claim 1, wherein the yellow toner is Pigment Yellow 74. In the method for producing a yellow toner for developing an electrostatic image containing a binder resin and colored resin particles containing a yellow colorant,
As the yellow colorant, one or two or more types of yellow pigments (A) whose pH of an aqueous suspension of the pigment measured by the boiling method defined in the pH meter section of JIS K5101 is 6 or more And a yellow pigment (B) having a structure of one kind or two or more kinds whose pH of the aqueous suspension of the pigment measured by the boiling method is less than 6.
The pH difference between the yellow pigment (A) and the yellow pigment (B) ([pH of aqueous suspension of yellow pigment (A)] − [pH of aqueous suspension of yellow pigment (B)]) is 0. 5. A method for producing a yellow toner for developing an electrostatic charge image, which is 5 or more.